Unstruck Barrel Weight question

[Liftengineerdoc]

Greetings!

I have a question on what, exactly, is meant by the term "Unstruck Barrel Weight". I've seen the term used frequently, but cannot find a concise definition of it. My Parker VH 12ga on No.2 frame has a lone 4 on the barrel flat.

Does this mean that if I took the barrels only, placed them on an accurate scale, that they should weigh 4 lb, 0 oz, assuming they've been unmolested since 1904 (IIRC) when the firearm was originally mfd? I doubt mine are in factory original condition, however, as the muzzle-end rib is fully zig-zagged to its end in front of the sight. The chokes gauge at I/M & Mod, not an uncommon pairing when the sky was the limit.

Also, what is the significance of the K f on the same flat?

I also have some older continental SxS with the same weight question, so this response may also kill several more birds 😁.

Thanks in advance!

Dale