My parents were Antique and Art dealers from before I was born. Dad's motto was: Every antique shop, flea market booth, estate sale and yard sale has at least one bargain in it. The trick is being smart enough to recognize it!
We had bought a large cardboard box of nazi items at an auction. There was a hand embroidered shoulder patch in with the stuff (which included the ultra rare "Successful Mission" U-boat tower banner). Dad let me just have the patch, because we couldn't identify it. Several years later I sold the patch to a collector that refused to identify the unit but paid me $3000 for it.
Always trust your gut!
Ivan