Unfortunately, I can't help as much with this one.

We have the same card, but it's not postmarked and I don't have a clue what the numbers mean.

We have another one from the same maker, also Golden Nugget, and the code in the stamp box is 16 at 180...also not postmarked.

We have a third one from that maker, also Golden Nugget, with the code 16 at 181, and it's postmarked October, 1949.

The Nugget opened in 1946....so I'd say 1946-1949.