I just bought my P40, and have a few questions. The first is that the back of the firing pin (that you can see from the rear of the slide) looks like a "half moon" it just looks like the bottom half of the firing pin, with no upper half, is that normal. I compared it to my P11 and the P11 is not like that. Second, my S/N is 752XX, anyone know about where that falls in the S/N range for P40's, and about how old it is?