mismatch pattern

[PatrickB]

A few years ago a bought a 1917 artillary in very good condition from a seemingly knowledgeable collector. The barrel, slide and all other upper components and the side plate were matching to each other. The frame and all other lower components were matching to each other. However, the frame and barrel number are different. The frame number is 1323d which may be 1916 rather than 1917. The barrel number is 3757g (I think it is a g but it is so stylized I'm not sure).

This fellow told me that the guns for a group of soldiers were often cleaned together and the upper assemblies and lower assemblies could become switched when many guns were disasembled and reassembled on the same table.

Is this pattern of upper and lower mismatch common? I guess there may be another artillary out there with the opposite mismatch.