Confusing Patent engraving on a 10K Gold, Ruby pin

[ssauble]

Looking through my grandmother's "lower end" jewelry, I stumbled upon this 10K gold ruby pin with a patent number that has left me a little confused.  The engraving on the lock seems to read, "PAT 5-17-10."

I've searched the patent database.  The number had been given to a gate lock in 1856.  Why would this be showing up on a lock for a pin?  And would it say anything towards its age?

Any input, insight would be very much appreciated.


Best wishes,
Stephan

[kerryandbee]

Just thinking out loud - could that be the date of the patent? A jeweler can sometimes tell the date of a pin by how its clasp is made.    KB