Recently I have acquired a 1956 book titled "Electronic Metal Locators". Quite a lot intersting reading for metal detectors enthusiasts. And even more in the bibliography given as an appendix.
I qoute it here OCR-ed:
"Metal locators for cows" caught my special attention.

Piotr
I qoute it here OCR-ed:
Bibliography - Periodicals
HOME-BUILT UNITS
· "Portable Metal Locator" by Harvey Pollack, Popular Electronics, June, 1955.
· 'Two Transistorized Metal Locators" by Edwin Bohr, Radio-Electronics, March, 1955.
· "A Modern Metal Locator "by Rufus P. Turner, Radio & Television News, September, 1954.
· "Small-Space Metal Locator" by John Haynes, Radio-Craft (now Radio-Electronics), September, 1948.
· "Electron Coupled Zero-Beat Metal Detector "by H. A. Fore, Popular Mechanics, August, 1946.
· "Try This 1946 Treasure Finder" by W. E. Osborne, Radio News (now Radio & Television News), Nov., 1946.
· "Metal Locator "by G. M. Bettis, Radio-Craft, April, 1943.
· "FM Metal Treasure Locator" by G. M. Bettis, Radio News, October, 1942.
· "Building a Modern Miniature-Tube Metal-Treasure Locator" by G. M. Bettis, Radio-Craft, December 1940; also June, 1941.
· "How to Make a Modern Radio Treasure Locator "by Allan Stuart, Radio-Craft, September, 1939.
· "Practical Metal Detector", Electronics, April, 1938.
· "Build Your Own Treasure Hunter", Radio News, Sep*tember, 1938.
· "An Improved Treasure Locator" by C. W. Palmer, Radio-Craft, August, 1934.
· "How to Build the New Treasure Finder "by E. F. Sarver, Radio-Craft, July, 1933; also November 1933 and April, 1934.
· "Radio Treasure Finder "by the Clyde J. Fitch, Radio-Craft, June, 1932.
· "How to Make Your Own Treasure Finder", booklet by Popular Mechanics Press.
· "Hidden Metal Detector" by Thomas A. Blanchard, Radio-TV Experimenter; Volume 3.
GENERAL
· "Underground Prospecting Tests with Radio Waves", Electronics, July, 1949.
· 'The Modern Divining Rod" by Alvin B. Kaufman, Radio & Television News, April, 1947.
· 'Treasure Finding Modernized" by W. E. Osborne, Radio & Television News, September, 1946.
· "Metal Detectors" by W. H. Blankmeyer, Electronics, December, 1943.
· "Finding Hidden Treasure ", Radio News, May, 1938.
· "Newest in Treasure Locators "by Gerhard R. Fisher, Radio-Craft, December, 1936.
· "Metal Locator Principles", U. S. Bureau of Mines Information Circular 6854 by J. W. Joyce, U. S. De*partment of the Interior. 1935.
COMMERCIAL APPLICATIONS
· "Pulp-Log Metal Detector "by M. Grobtuck and D. J. Williams, Electronics, July, 1952.
· "Industrial Metal Detector Design "by Curtis R. Schafer, Electronics, November, 1951.
· "Choosing Industrial Metal Detectors" by C. R. Schafer, Electronics, June, 1951.
· "Detecting Tramp Metal in Logs and Iron Ore" by C. W. Clapp, Electronics, March, 1951.
· "Metal Detector for the Lumber Industry" by Curtis R. Schafer, Electronics, September, 1949.
· "Metal Detector for Conveyors" by Kenneth Urbach, Electronics, July, 1949.
· "Development of Locators of Small Metallic Bodies" Journal of Institute of Electrical Engineers, Dec.,1948.
· "Metal Locator for Cows ". Electronics, May, 1948.
· "Detectors for Buried Metallic Bodies" by L. F. Curtis, Proceedings of 1946 National Electronics Conference.
· "Electronic Locator for Salvaging Trolley Rails" by J. G. Clark and C. F. Spitzer, Electronics, Jan., 1944.
· "A Practical Metal Detector" by W. C. Broekhuysen, Electronics, April, 1938.
· "An Electromagnetic Metal Detector" by D. G. C. Luck and C. J. Young, RCA Review, October, 1936.
MINE DETECTORS
· "How Mine Detectors Work" by Eric Leslie, Radio-Craft, July, 1949.
· "Mine Detectors "by Andre Violet, Electrical Communi*cation, March, 1948.
· 'Vehicular Mounted Mine Detector" by H. G. Doll, M. Lebourgh, and G. K. Miller, Electronics, January, 1946.
· "Non-Metallic Mine Locator" by T. E. Stewart, Elec*tronics, November, 1945.
· "Locating Land Mines" by Paul Horni, Electronic In*dustries, January, 1945.
· "Mine Locators" by Connery Chappell, Radio News, March, 1944.
BOOKS
· "Geophysical Exploration" by C. A. Heiland, Prentice-Hall (Out of print).
· "Exploration Physics "by J. J. Jakosky, Times Mirror Press.
· "Imperial Geophysics" by A. S. Eve and D. A Keyes , Cambridge University Press.
· "Applied Geophysics" by A. S. Eve and D. A. Keyes, Cambridge University Press.
· "Buried Metal Detectors" by W. H. Blankmeyer.
BOOKS AND ARTICLES ABOUT TREASURE (Courtesy of W. H. Blankmeyer)
· "Buried Treasure" by Ken Krippene, Permabooks, 1950.
· "Lost Mines of the Old West" by HowardD. Clark, Ghost Town Press, 1946.
· "Treasure Trove" by J. F. Dobie, Literary Guild, 1931. Lost southwest mines and buried treasure.
· "Treasure Hunting" by Harold T. Wilkens, E. P. Dutton & Company.
· "Pirate Treasure "by Harold T. Wilkens, E. P. Dutton & Company.
· "Legends of Texas" by Frank Dobie, Texas Folklore Society, 1924.
· "Book of Buried Treasure "by Ralph D. Paine, Mac-millan, 1926.
· "Doubloons" by Charles B. DriscoU, Farrar & Rinehart 1930.
· 'South For Treasure "by William LaVarre, True Mag*azine, August, 1949.
· "Treasure Hunter" by Harry E. Rieseberg, Mcbride, 1945. True undersea treasure hunting and adventure and development of undersea apparatus.
· "Captain Kidd and His Skeleton Island" by Harold T. Wilkens, Liverright Publishing Corp., 1937.
· "They Found Gold" by Hyatt Alpheus Verrill, G. P. Putnam's Sons, 1936. Stories of success treasure hunts.
· "Pirates Ahoy" by Charles B. Driscoll, Farrar & Rinehart, 1941.
· 'Treasure Express" by Neill Compton Wilson, Mac-millian, 1936. Stories of Wells Fargo days.
· "Treasure Trove" by Ralph Delahaye Paine, Sturgis Walton Co. 1911. Tales of buried gold, jewels, and plate that is still being sought.
· "Lost Mines and Buried Treasure" by Robert G. Fergu*son, Fisher Research Corp. Palo Alto, Calif.
· "Apache Gold and Yaqui Silver" by Dobie, Bailan Books.
· "Gold of the Supersititions" by Barry Storm, Fisher Re*search Corp. Palo Alto, California.
· "Dive For Treasure" by Lieut. Harry Rieseberg, New Liberty Magazine, Medical Arts Building, Guy and Sherbrooke Sts. Montreal, Que. Story of Port Royal-Pirates Haven.
· "I Hunt Ghost Gold" by Oren Arnold, Sat. Evening Post, Dec. 28, 1946
HOME-BUILT UNITS
· "Portable Metal Locator" by Harvey Pollack, Popular Electronics, June, 1955.
· 'Two Transistorized Metal Locators" by Edwin Bohr, Radio-Electronics, March, 1955.
· "A Modern Metal Locator "by Rufus P. Turner, Radio & Television News, September, 1954.
· "Small-Space Metal Locator" by John Haynes, Radio-Craft (now Radio-Electronics), September, 1948.
· "Electron Coupled Zero-Beat Metal Detector "by H. A. Fore, Popular Mechanics, August, 1946.
· "Try This 1946 Treasure Finder" by W. E. Osborne, Radio News (now Radio & Television News), Nov., 1946.
· "Metal Locator "by G. M. Bettis, Radio-Craft, April, 1943.
· "FM Metal Treasure Locator" by G. M. Bettis, Radio News, October, 1942.
· "Building a Modern Miniature-Tube Metal-Treasure Locator" by G. M. Bettis, Radio-Craft, December 1940; also June, 1941.
· "How to Make a Modern Radio Treasure Locator "by Allan Stuart, Radio-Craft, September, 1939.
· "Practical Metal Detector", Electronics, April, 1938.
· "Build Your Own Treasure Hunter", Radio News, Sep*tember, 1938.
· "An Improved Treasure Locator" by C. W. Palmer, Radio-Craft, August, 1934.
· "How to Build the New Treasure Finder "by E. F. Sarver, Radio-Craft, July, 1933; also November 1933 and April, 1934.
· "Radio Treasure Finder "by the Clyde J. Fitch, Radio-Craft, June, 1932.
· "How to Make Your Own Treasure Finder", booklet by Popular Mechanics Press.
· "Hidden Metal Detector" by Thomas A. Blanchard, Radio-TV Experimenter; Volume 3.
GENERAL
· "Underground Prospecting Tests with Radio Waves", Electronics, July, 1949.
· 'The Modern Divining Rod" by Alvin B. Kaufman, Radio & Television News, April, 1947.
· 'Treasure Finding Modernized" by W. E. Osborne, Radio & Television News, September, 1946.
· "Metal Detectors" by W. H. Blankmeyer, Electronics, December, 1943.
· "Finding Hidden Treasure ", Radio News, May, 1938.
· "Newest in Treasure Locators "by Gerhard R. Fisher, Radio-Craft, December, 1936.
· "Metal Locator Principles", U. S. Bureau of Mines Information Circular 6854 by J. W. Joyce, U. S. De*partment of the Interior. 1935.
COMMERCIAL APPLICATIONS
· "Pulp-Log Metal Detector "by M. Grobtuck and D. J. Williams, Electronics, July, 1952.
· "Industrial Metal Detector Design "by Curtis R. Schafer, Electronics, November, 1951.
· "Choosing Industrial Metal Detectors" by C. R. Schafer, Electronics, June, 1951.
· "Detecting Tramp Metal in Logs and Iron Ore" by C. W. Clapp, Electronics, March, 1951.
· "Metal Detector for the Lumber Industry" by Curtis R. Schafer, Electronics, September, 1949.
· "Metal Detector for Conveyors" by Kenneth Urbach, Electronics, July, 1949.
· "Development of Locators of Small Metallic Bodies" Journal of Institute of Electrical Engineers, Dec.,1948.
· "Metal Locator for Cows ". Electronics, May, 1948.
· "Detectors for Buried Metallic Bodies" by L. F. Curtis, Proceedings of 1946 National Electronics Conference.
· "Electronic Locator for Salvaging Trolley Rails" by J. G. Clark and C. F. Spitzer, Electronics, Jan., 1944.
· "A Practical Metal Detector" by W. C. Broekhuysen, Electronics, April, 1938.
· "An Electromagnetic Metal Detector" by D. G. C. Luck and C. J. Young, RCA Review, October, 1936.
MINE DETECTORS
· "How Mine Detectors Work" by Eric Leslie, Radio-Craft, July, 1949.
· "Mine Detectors "by Andre Violet, Electrical Communi*cation, March, 1948.
· 'Vehicular Mounted Mine Detector" by H. G. Doll, M. Lebourgh, and G. K. Miller, Electronics, January, 1946.
· "Non-Metallic Mine Locator" by T. E. Stewart, Elec*tronics, November, 1945.
· "Locating Land Mines" by Paul Horni, Electronic In*dustries, January, 1945.
· "Mine Locators" by Connery Chappell, Radio News, March, 1944.
BOOKS
· "Geophysical Exploration" by C. A. Heiland, Prentice-Hall (Out of print).
· "Exploration Physics "by J. J. Jakosky, Times Mirror Press.
· "Imperial Geophysics" by A. S. Eve and D. A Keyes , Cambridge University Press.
· "Applied Geophysics" by A. S. Eve and D. A. Keyes, Cambridge University Press.
· "Buried Metal Detectors" by W. H. Blankmeyer.
BOOKS AND ARTICLES ABOUT TREASURE (Courtesy of W. H. Blankmeyer)
· "Buried Treasure" by Ken Krippene, Permabooks, 1950.
· "Lost Mines of the Old West" by HowardD. Clark, Ghost Town Press, 1946.
· "Treasure Trove" by J. F. Dobie, Literary Guild, 1931. Lost southwest mines and buried treasure.
· "Treasure Hunting" by Harold T. Wilkens, E. P. Dutton & Company.
· "Pirate Treasure "by Harold T. Wilkens, E. P. Dutton & Company.
· "Legends of Texas" by Frank Dobie, Texas Folklore Society, 1924.
· "Book of Buried Treasure "by Ralph D. Paine, Mac-millan, 1926.
· "Doubloons" by Charles B. DriscoU, Farrar & Rinehart 1930.
· 'South For Treasure "by William LaVarre, True Mag*azine, August, 1949.
· "Treasure Hunter" by Harry E. Rieseberg, Mcbride, 1945. True undersea treasure hunting and adventure and development of undersea apparatus.
· "Captain Kidd and His Skeleton Island" by Harold T. Wilkens, Liverright Publishing Corp., 1937.
· "They Found Gold" by Hyatt Alpheus Verrill, G. P. Putnam's Sons, 1936. Stories of success treasure hunts.
· "Pirates Ahoy" by Charles B. Driscoll, Farrar & Rinehart, 1941.
· 'Treasure Express" by Neill Compton Wilson, Mac-millian, 1936. Stories of Wells Fargo days.
· "Treasure Trove" by Ralph Delahaye Paine, Sturgis Walton Co. 1911. Tales of buried gold, jewels, and plate that is still being sought.
· "Lost Mines and Buried Treasure" by Robert G. Fergu*son, Fisher Research Corp. Palo Alto, Calif.
· "Apache Gold and Yaqui Silver" by Dobie, Bailan Books.
· "Gold of the Supersititions" by Barry Storm, Fisher Re*search Corp. Palo Alto, California.
· "Dive For Treasure" by Lieut. Harry Rieseberg, New Liberty Magazine, Medical Arts Building, Guy and Sherbrooke Sts. Montreal, Que. Story of Port Royal-Pirates Haven.
· "I Hunt Ghost Gold" by Oren Arnold, Sat. Evening Post, Dec. 28, 1946

Piotr