It's a miracle that you photographed the siderail at all, - it is impossible to tell the exact ranges of this feature (blank siderail=BSR) due to the fact almost no one photographs or records a area where a marking doesn't exist, - even though many know that it once existed or could exist in this area... a mere small fraction even take a picture of the most important angle a rifle has, - the right receiver on early production - even when acceptance is there.
Your rifle has a BSW barrel, it is fairly common in this rifles range, your receiver is Walther made, should be e/359 x1, e/37 x2 on the right receiver, the siderails are blank for part of 1941, though it is hard to be accurate to the extent as so few take this angle when they have a siderail marking, needless to say when it is blank.
JPS (147 - ce) started production without siderails (BSR) from 1934 and into 1936, then it varies and seems to date to the time e/116 changes to e/359 for the receiver hardened position, Vol. I might cover this in detail as to why and the exact ranges Mike observed. Mod.98 stays until the 1st block of 1941, - so far I have not been able to confirm a 147/1940, even in the last blocks without a SR, though one might exist.
In the 1st block of 1941 they intermingle it seems, how common is impossible to say as of the 12 recorded only 3 show the SR, two have them and one do not, the “a” block is similar, some have them others do not, but the reporting is sparse. This BSR last for a short range, how long is impossible to say as probably not 25% show the feature, even when reported by experienced collectors. It seems to come back in the ce/41 "g" block but is intermittent at least to the "h" & "i" blocks where both Mod.98 & BSR exist.
It is like pulling teeth to get even experienced collectors to show the right receiver and siderail consistently, I have to ask at least 50% of the time, - the inexperienced or on auctions you expect this lack of images, especially when the areas are "probably" blank, but this kind of information is very unreliable as such things can only be determined if they are imaged.
Of course Mike might have more information as I assume he will cover it in Volume II.
