Regarding the interchangeable principal on the Webley & Scott, 400 Series, 'The History of W. & C. Scott Gunmakers', by Crawford & Whatley, states on pgs. 65 & 68, "Webley & Scott introduced the Proprietary hammerless boxlock, later called the Model 400, in 1900. The Proprietary boxlock was one of several Webley & Scott models designed on the interchangeable principle. Virtually all of the major British gunmakers of this era used machines for the initial shaping of parts, but the interchangeable principal took the use of machines an additional step. The components of the gun were machined to precise dimensions to reduce time required for assembly of the gun and to facilitate replacement of worn or broken parts. Final fitting of parts, stocking, and finishing were all performed by hand."
