Anything which is pre-1930, and has a hooded scope, and the newer
barrel bands, was re-arsenaled in 1930(ah, "91/30"...). A true shame, as
an un-arsenaled 1891 is considerably more valuable. At that point,
bad stock parts were replaced, and the entire rifle was brought up to specs.
Great for the Russian MOD, not so hot for us collectors.
The Terry Lapin book will tell the serious collector everything that is
known, but many factory stamping's meanings were lost in the sands of
time, as JonM indicated.
Of particular value now, is an 1891 Dragoon of Czar Nicholas era, which hasn't
been re-arsenaled, and hasn't had the Empire Crest obliterated, as most
were, after the Great Revolution.