It's not "self-evident" because there is a mixture of genuine old ashtrays, AND new ashtrays with closed casino names. I should say "name" because the only new trays I remember seeing were "from" the Silver Slipper. There was no marking ON the 'tray to indicate it was a reproducion, I didn't see any sign advertising it as "honoring" an old casino.....the ONLY indication that it was a newly made ashtray was the $12 price tag. As an ashtray collector, I've never seen a tray of that design (triangle) from the Silver Slipper....but "new" (old) trays still appear pretty often.
We've also seen fakes on eBay. It's not as bad as chips yet, but it's heading in the same direction