I have recently acquired a 325B .30-30 and need some info about the rear sight. It is not the Dockendorff dial-type rear sight, but the notched twin-ramp variant. Does anyone know what increments these were graduated in, and, if so, at what range they start?

Incidentally, I would also like to know, if possible, when, in the 1947-50 life cycle of the 325, was the "B" produced? Mine either has no serial number or it is so well hidden that neither I nor my dealer could find it, so dating it that way is a non-starter.

Any help is appreciated.