That story rings a bell... I think we had something like that as well — it was plastic though, and was used to scrape off the scratch-and-sniff coating to see how much we’d won or whatever (we won nothing of course).
I’ve got it in front of me now.
It’s a little smaller than a 50-cent piece. The heads side says “Augustus Pater” around the head, and the reverse has what looks like 2-column arch with fasces inside, with S and C bordering it on the outside, and “PROVIDEN” underneath.
It feels like metal and is heavier than a quarter, so I think it is metal, but I’ve never used it to scratch off prize tickets, so I can’t be sure!.