Hendere, here are 2 shells from my collection. I think you’ll agree that they are identical to yours but brighter. While yours may well be from the 20’s, I wonder if they were just poorly stored and the ‘ageing’ is from adverse contact with the elements? Mine are from the early 1960’s and made for the Western Auto Company by Federal. The box is marked ‘Revelation’, a trade name used by Western Auto. These shells are also identical to the Federal Hi-Power shells of the same period, 1950’s and 1960’s. Mine, like yours, are roll crimped and have 6 on the over-shot wad.