Thanks for the PDF. I hope you don'r mind that I downloaded it for further reading. I read the appropriate areas and they mention cord wear, but it is interesting that it mentions damaging the chamber, not the crown. (perhaps due to the presence of a guide) I don't know how pulling a cird off center would cause the back end of the pull through to damage the chamber but......I think the mark is a
*
W
An asterosk over a capital W..but I've never seen a rifle so marked. I'm guessing the barrels were changed out as soon as possible. Here's a link to 1931 Armourer Instructions. Cord wear is referenced on page 8. But not the mark.
http://www.vcrai.com/INSTRUCTIONS_FOR_ARMOURER1.pdf
More interesting is that muzzle wear is identified as resulting from improper use of a hardened steel rod. I'm with them on that. It's a holiday here and I'm pressed for time. I hope I read the above correctly. In any event, thanks again. ~Muir