I don't think that's any more mysterious than it was probably part #35 in 1899. The receiver, screws, etc go up to 31.
The crescent buttplate is listed as part #35 into the 1930's. In an early 1920's parts catalog it's -
"1 B 35 Butt Plate Reg. Rifle Steel..... 1.25" I don't know what the "1 B" means.
I pulled an 1895 case-hardened buttplate and tried it on an 1899 circa
1918 1919 and it fit really close with very small gaps in places. I also pulled the buttplate off a Marlin Model 1893 and it fit the Savage 1895 almost perfectly. None of the three buttplate had numbers cast in them but they all have serial numbers stamped on them, not sure if Winchesters would. (I didn't think to take pictures when I had them all off......)
Thank you, Gene! Was busy that day.
It's 35 in the 1897 catalog.
35 in the 1900 catalog.
35 in Catalog 60.
It's "1 B 35" in Catalog 61.
Still 1 B 35 in the 1942 parts list.. and in the 1946.. and 1948.. Don't have any parts diagrams from the 50's organized.
I think that's enough to settle it.
Interestingly, the early shotgun buttplate was part 35A.
By catalog #60 the shotgun buttplate was part 35 1/2 (serrated different than smooth?), and hard rubber buttplate on the 1899H was part 35 3/4.