An excellent classic period rifle of high quality, the only difference of "quality" in this case being the level of engraving

The percussion style fences are my personal favourite (especially considering they were cut by hand!), and the high hammers that are usually circa 1970, medium and lower hammers being later

The London proofs are post 1855, the variations after are more relevant to shotguns The 40 bore is .488, and close enough for the .577/500 No.2, a good all round cartridge, popular in India for everything except perhaps elephant

I have a double "Howdah" rifle (posted here somewhere) and a WR "Improved Martini" in that calibre

Desirability of calibres is personal, although a full .577 BPE (or Nitro!) generally commands a premium

The difference between .450 - 3 1/4" and .577/500 N0. 2 is personal and equably desirable, manufacturer and condition being more important, McNaughton being top quality

You certainly have a very desirable DR and good luck if you are going to shoot it

TH