I am an FFL and I recieved a nice Rapid Fire 1919a4 for a customer of mine. When I open the top cover and pull the bolt back I see the engraving that says it was made by Rapid Fire. I am having trouble locating a serial number. The top cover has a serial number, but I understand the serial should also be on the side plate. These are very different from what I usually see around the shop. 