During the lock down I have been going thru a bag of coins that has been on my desk for I can't remember how long. They have mostly been filed with reasonable idea of what they are. This one has me stumped. A search got me here, but it did not help find anyplace that helped much.
https://www.coincommunity.com/forum/topic.asp?TOPIC_ID=143478

The triangle has everyone stumped it seems.