Some barrels are remarked when work is carried out, on guns converted from muzzle loaders to breach loaders sometimes the names on the locks will show the original maker and the barrels will read

" converted by (then the smiths name) "

When guns are rebarreled sometimes they read

" replacement barrels by ( then the smiths name ) "

The same is occasionally done when guns are sleeved, if its not showing evidence of work ie the barrels just say "Westley Richards" and the action says something different i would assume its something that's been cobbled together.

In the former circumstance where the engraving is evidence of a guns history i'm rather partial to them.

The engraving on this gun tells the guns whole story - started in 1835 as a muzzle loader, then converted, and then re done as a presentation piece with solid silver furniture in 1882, then has been nitro proofed and survived that.