Thanks Mitch. Didn't find it between the ears or behind the extractor, but curiosity got the best of me and I dropped the side plate. It was stamped there as well. Because the ears seem to be integral with the rest of the frame it doesn't bother me. So it looks like the only place I'm missing is the back of the extractor. That could have been a mistake of an assembler who didn't mark it, or a replacement extractor. Internally the gun was really clean. There's no way I'm going to take down the pivot point. I made that mistake with an Enfield revolver, and after a week and much anxiety it was back together.