I too have a No 51, according to the serial number and AYA's quick reply. They advised me that it is lower quality that a No 2. I bought it from Paul Crosnoe for a customer but it turned out to have factory left hand dimensions so the customer couldn't use it. I'm a southpaw so I kept it for myself. My gun has a short beavertail fore end which I generally don't like, but this gun is growing on me because I don't miss much with it.