Bob and Miller,
Thank you both.
Under glass, what I thought was an "F" turns out to be unfinished at the bottom. A short distance way, as Miller notes from the photo, is what looks like the point of the bottom bar of an "E." That little mark has clearly been stamped in the metal, suggesting that "E" is a real possibility.
Wonder if a factory error caused someone to mis-stamp an F-grade purchase, s/n 11885, on the barrels as an E with the 5 badly stamped as well, and the factory decided to use the mis-stamped barrels for the C-grade second pair, adding the s/n of the C-grade to the other tube. A new and correctly stamped set of barrels likely went to the F grade 10 bore that Bob has recorded.
Interesting.
Regards, Tim
