Interesting! I know the house was built around 1956 , Ive only been in it a couple years not sure what was here before But I had heard alot of fill was put in to level so I guess no telling what could be there
Looks like your yard has a lot of potential. I believe Tony in SC is correct about the whatsit being the finger ring part of an old candle holder. I have found 2 like it in the past. Stay safe and keep swingin.