Could it be rifle serial number?
If he was born in 1932, he woud have started his service in 1950-1951, the number corresponds with a 1951 serial number.http://www.radix.net/~bbrown/schmidt...ml#manufacture.

I can't remember if the stocks have serial numbers in thebarrel channels or not, but usually the year of manufacture is stamped under the butt plate, the yea rof manufacture is also usually stamped on the receiver tang and/or bolt. I have two mismatched rifles- one with a replacement bolt and another with a replacement stock, so it does happen with swiss rifles.