Until we find a 10-gauge hang tag or two it is all conjecture, and we can each conjecture any way we want!! There are some interesting inconsistancies in the hang tags, like this one pictured in Charles' book --
It gives loads for all three gauges on the back, but doesn't mention the amount of shot in the loads, just powder charges?!? On the front of the tag it says the gun was targetted with load X8, 24 grains of Infallible pushing 1 1/4 ounce of No. 8 chilled shot, in a 2 5/8 inch Nitro Club shell. However, in all my UMC catalogues from 1903 on, load X8 is only offered in a 2 3/4 inch or longer shell?!?