1939 K98 Mauser help

[GUTS]

It's a flat buttplate, and if original to the barreled action is correct for a code 237, 1939 Berliner-Lubecker-Machinenfabrick produced rifle. This factory didn't change to cupped buttplates until the "m" serial numbered rifles in the middle of 1941. That is a nice Luftwaffe stock also, if it's from the rifle it should be numbered in the barrel channel with at least four of the serial number. 1939 was also the first year that laminate stocks and handguards were used at factory 237, before that they are all solid walnut.