i dont think rule 11 should apply to mill surplus arms and antiques, well i think the picture part should though
can you imagine a "lee enfield 303" add (just an example)
trying to figure out all parts changed and modded over the years from the first time it left the "original factory".
there would be any and all Armorer repairs after it left "original factory", FTR's after it left "original factory", bolt head changed to get proper head spacing, for ends cut down, front sights changed, screws changed because of stripped heads, butt pads installed, factory repairs to the wood, if the brass disk in the butt stock was original, its endless,
i think the buyer should be the one to figure all that out if the add said " lee enfield 303"" dont assume its 100 % original all matching. the sell may not know what he has and is just looking to get rid of it, buyer does know what he wants though.
but in this case, if the gun was complete in original trim but wasn't matching i would put it in the add, if i knew what i had and it wasnt matching. like the OP did.
i don't think anything should be hidden though, any damage or make shift parts should be listed. as for matching numbers, i my self would put it in the add because i know that's what people want to know about it, but i remember selling some surplus rifles that were clearly sporterized and never mentioned if they were matching or not
but the buyer should ask if the item is actually what he wants if the pics don't show it is.