As far as I know only one of these existed until today. Rick Minor had it in his collection. I considered it an error until today. IMO, They are no longer errors. There is a Black and a Blue Mint $1.
This brings a complete Borland set with opening and closing dates to 83 different.
This one is not for sale or trade and I only have 1. I did see more but its not my place to say where they are.