Over on the jewelry forums on ebay, lots of interesting questions and dilemmas come up and lots of nice folks are very helpful.   Imageelf has allowed me to copy the fotos from a question posed recently about the patent for earring clip backs.  Thanks Imageelf!!  

Basic patent info:  Patent by Frederick W Moulson, Assigned to B.A. Ballou & Co  Application May 14, 1949,. patent granted Dec 13, 1949

What was interesting to me about this patent is that the actual production of the patent differs from the design drawings a little bit.   These earrings are marked with the patent number.  And since this patent is  a design patent rather than a utility patent, normally it seems that it should be pretty darn close!     The reason I find it interesting is that when we are trying to research an item and using patent drawings to match to an actual item, you wonder just how far the actual item can deviate from the drawing and still be identified accurately.   okay, that sounds confusing.  What I mean is,  if you are looking at an earring (in this case), that doesn't have a patent number written on it, and are trying to identify the patent that goes with it to help identify its age or manufacturer, how close does it have to match to feel confident that you have identified it correctly? 

Here are the fotos and patent drawing, so you can see the differences.   Imageelf noted two main differences that she saw.  First she noted that the number of little "petal" shaped openings at the end of the clip are different. The patent drawing shows 4, but the earrings only have 3.    In addition, at the hinge end, the drawing shows a solid piece under the hinge, where on the earrings, it is actually open (kind of a "c" shape).     

So, if you saw these earrings, and then saw the patent drawing, would you say they match?  I'd probably hesitate.  But since they are marked with that exact patent, they do in fact "match" for identification.  

Note these (thanks to jewelrybypaula for the pics!) have sharp points added, so that they can presumably be used for dress or fur clips.