I recently had a Webley & Scott boxlock non-ejector that was built circa 1910 and was marked 1 1/4 oz. nitro proof and upon measurement was definitely 2 1/2" chambered. Why? Who Knows...
Over the years have seen several inconsistencies. Considering the hundreds of thousands of guns processed,the odd case of human error is not surprising.

Better to keep your mouth shut and be thought stupid,than open it and confirm.