If I find a piece of Bill’s art on the secondary market what should I look for?

When Bill was just starting out, he usually put a date and the S Slash V brand (an old family brand which belonged to Bill’s Uncle) in the area where he signed the piece.

When you find a piece signed in this way, it’s a very early piece and was created prior to Bill becoming a member of the Cowboy Artists of America. When he became a member in 1973 he quit using the S Slash V brand and began putting the CA brand on his art.