I have a pair of vintage ear clips that I thought were marked and now as I'm seeing the tiny print - it says PAT PEND. I'm assuming that means patent pending but what does that mean to vintage jewelry?
There are design patents and there are utility patents. No doubt your PAT PEND mark is an indication that the utility patent for the clip mechanism on your earrings had been applied for. Utiltiy patents, once granted, are good for 17 years. Once patents expire, if not renewed, anyone can copy that design.