Stripper Clip Headstamps

[vp146b4]

Looking close at some old 1903 Springfield, I think, stripper clips. They are parked and have "SEY" headstamp. I then looked at some steel, unparked ones, and they had a "H" headstamp. First, are they Springfield clips, or are they something else? Second, where could I find a link to help indentify the headstamps?
Thanks,
Bill

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