That was pretty common with the early Bud Jones coin in center chips. I don't know if it was intentional or just a variation while mixing the dye during manufacture. This was seen on many $5 coin in center chips used in Atlantic City at Harrah's Marina, Claridge, Harrah's at Trump Plaza and Playboy. The chips that you show are from the "dig" and the variation could also come from being buried for years.