"Many talented coin engravers, as well as newcomers, started creating hobo nickels in 1913, when the Buffalo nickel entered circulation. This accounts for the quality and variety of engraving styles found on carved 1913 nickels. More classic old hobo nickels were made from 1913-dated nickels than any other pre-1930s date.
Many artists made hobo nickels in the 1910s and 1920s, with new artists joining in as the years went by. The 1930s saw many talented artists adopting the medium. Bertram Wiegand, known almost exclusively as Bert, began carving nickels in the teens, and his student George Washington Hughes, known as Bo, began carving in the late teens (and up to 1980). During this period, Buffalo nickels were the most common nickels in circulation." -- La Wik