Can you get anything off of the headstamp? All brass shells have been around for a LONG time. They were advertised in the 1869 UMC "catalog" and have been around undoubtedly before that. The headstamp will help determine the date range for your specific piece. It is a nice find!
Without seeing the headstamp itself, all I can do is guess. My best guess is it is a Winchester and probably one of these varieties.
If this is the case, the tightest date range I can get is 1879-1949 as the headstamp did not change during the lifetime of this particular line. Once again, nice find