Could be a replacement part for a Ruger first gen Vaquero or Blackhawk depending on the length. Ruger sells these as replacements. I believe the Ruger New Vaquero, blued, now comes with a steel one as well.
All my blued NM flattops and New Vaqueros have steel ejector housings including the 50th anniversary ones. I actually bought steel ones as replacements on other standard NM BHs. So could have been off a lot of different Rugers including SBHs .
each one has an application or time frame of they were used and if in nice shape, there is always someone looking for one, handy to have ,,,just compare them up against some others you may have on any guns, to "see" any differences, such as size over all, and of the hole for the screw, etc..... the steel ones are very simple and easy to restore, refinish, and the aluminum ones need to be addressed as to the finish wanted, available, or able to do yourself.....