Bach trumpet serial number dating
If you look at the serial number list page, the few horns that have purchase dates claim that these are late 1940s to mid 1950s.
This also shows better the style of mouthpiece that came with them.
Below is Muck #1739 then next is Bach #3382 from about the same time period. #1774 #1779 #1866 #1869 French Bell Rim models: This next group looks to have the same valve section as the Bach copies yet the top and bottom caps have changed and the bell rim has a French style which wraps over the rim another 1/8" back up the bell.
The lead pipe inlet changes and the water keys have a square saddle base. #1005 - this one seems to be out of sequence but who knows with Muck #2033 #2101 courtesy of Joe Alacqua - purchased in late 1957 - the bottom caps are not original #2184 #2187 #2386 - author's collection - vertical Citation with simply engraved US logo - this has two engraved lines around the bell which match the late 1950s Carl Fischer ad below At this time Carl Fischer owned both Muck and York so I found these two examples to see if the old York plant was the source.
For example, in 1928 the Apollo serial numbers were 8600 - 8700.
In 1939 the Mercury models had serial numbers in the 10,000s. Vincent Bach used the trade names of Stradivarius, Mercedes, Mercury, Minerva, and Apollo.