Very fine re-inforced top lever action. possible to have a new set of barrels made in say .450 nitro keeping the "original" barrels as is.

Not worth 30 K in my opinion. Your $500 offer might be a bit light, however.

Purdey hammerless double rifles are very scarce with only about 500 ever made in all grades and locking methods.

All the best, Mal