Interesting Bob, and thanks for posting.
It's a lower quality 2 Iron "Horse-shoe" Crolle pattern with a section of the ribband at the right breech that wasn't twisted, and the left with only a few twists. The breech section 'lopin' or billet started out as alternating thin plates of 3 iron and 3 steel with a thicker 'bloom' of mixed steel and iron in between.
Never seen anything like it, and will be adding it to the 'Damascus Anomalies' PictureTrail album

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