Diamond-studded silver key. Not commercially minted. Looks to actually open something. Not plated. Not magnetic. We have many monasteries around here. Could it be a drop?
I dont see an exact match but it looks like a crown key pendant. Is it gold or silver? View attachment 635499
"This is a diamond crown key necklace, which will surely set her off. It is adorned with pave diamond insets. It has a lobster lock closure and is made in the USA."