I believe it would be unwise to purchase a vintage double, of any maker, without knowing, or being able to measure accurately oneself the end of chamber, forcing cone, 9 from breech, 9 from muzzle, and exactly where the MWT is found.
And breech to muzzle bore measurement looking for a bulge not apparent on external examination.
Bad things happen to good guns after 100 years or so.
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/editBro. Toby's "Eiffel Tower" profile is well said and fits my experience with U.S. makers also
Standard dimensions of each barrel tested as part of the 1891 Birmingham Proof House Report from "The Field" March 7, 1891 Vol 77:325
http://books.google.com/books?id=inQCAAAAYAAJ&pg=PA9 NOTE: these dimensions do NOT represent MWT, but show the "Eiffel Tower" profile. The chambers are not cut nor do the barrels have choke constriction

Mark Twain
It is better to be careful 100 times than to get killed (or kill a bystander with a chunk of shrapnel) once.