I don't think the grooved hammers found on 1917's are the same as the ones found on RM's. I believe the grooves on the sides are the same but the checkering on top differs (if I recall correctly). I have never been fortunate enough to have an early 1917 (yet) so I'm going from memory. I do have a pre war outdoorsman that has a grooved humpback. I thing another forum member (Jerry maybe) also has one with same grooved hammer from the same late serial number range (62000 IIRC). I think they may be factory but shipping records missing per Mr. Jinks.

Roger