Thanks for the info.
I thought about a backup for the $500 but discounted that because of where they came from.
And, the first comment from showing it to BJ people was, in the 90's they experimented with the cross hatching to keep people from complaining about them being too slippery. So I settled on the word prototype until I get more info.
Hopefully the records search will tell us.

What value do you put on the $500? I can get 6 of them.

Only 1 of the $5,000's and 1 plaque.
I sent all 3 to TCR authors.