Roy, these are CHIPCO manufactured chips, which used a dye-sublimation printing process. Chip designs were printed onto a special paper, using special ink, in a reverse image. The printed sheets were placed against blank, ceramic chips and with heat and pressure, the reverse image inks were transferred to the blank chips.

The chips you are showing were printed onto twice, in what was most likely a cancellation effort, or possibly in error. It is difficult to tell which image was pressed first, because on the second printing, the inks on the paper and the inks already on the chips, will mix and creat other colors. If you recall your color mixing from kindergarten, yellow and blue make green. Note the yellow letters of "EL SAN JUAN" and the blue background of the Buffalo Chip have mixed to green on the overprinted chip on the left.

Jim