Remington and Union Metallic Company existed from 1911 until 1934. So your REM-UMC shot shell is from that period. Remove that clump of dirt to reveal the gauge of the shell. You will probably find more shells so here is a very good site to help you ID them:
1915-1937. The date range is directly from original Rem-UMC catalogs. The 1937 catalog states the Nitro Club line of shells is being discontinued and it is not in the 1938 catalog, so it is no later than that.