Yet another theory. Did Borland have the old stock from Bud Jones? Perhaps he found a box of one sided Jolly Trolly 50¢ chips, and then just stamped the other side, with the Silver Slipper die he had.

Perhaps the factory was working on an order, using that color chip and finished, but they had already done one side of some of the chips. They went back into inventory, in case of a future order. Which never happened, so Bug Jones had a bunch of one sided sample chips, or test chips.

Is the chip coin aligned? Borland was known for doing precise alignments on his chips.