Greetings,
my brass clips are dated SMI-28 & LN-C17
From another site that deals with military rifles, I was told they are 1917 and 1928 production.
later clips are steel....SMI-39 of which I have 3 and 1 stamped RR-M36.
(1939 and 1936)
some folks actually ''collect'' these clips.
there are some ''aftermarket'' clips available (reproductions) that are reported to not function very well.
Again, all the ''original'' clips I have function without any trouble in both my old 1891 long rifle and my like new model41 (FAT47),.
hope this is of some help.