I filled a few holes in my Borland collection for $1 each at GGS in 1998. That is when GGS bought out the Bulk of the Borland chips.
GGS sold out 1,000's of them in a few months or maybe weeks.
I have a complete set of 82 different.

Lay off Spragg. If the Black Mint $1 is real its an error at this time. Not part of the set IMO.