Thank you for the invitation jmoore, but there's not a lot to add to what you have already written.
Firstly: the Moschetto M38 d.c. was in 7.35 mm and fitted with the simple fixed backsight. And in Brescia it was apparently only made in this form in 1938, in the series range Ixxxx. But things got complicated later....
This looks like an Moschetto M91 d.c. with the adjustable backsight, and should therefore be in the usual 6.5 mm Carcano chambering.
So how is this to be explained?
The answer is, the Itaians 1) abandoned the 7.35 mm under the pressure of war requirements, and 2) abandoned the fixed backsight in 1940, going back to the sight which you see here, and then introducing the M91/41 which finally abandoned the gain-twist barrel. And some of the 7.35mm M38s were also converted back to 6.5mm. Plus some were made with new barrels and some were converted from old M91 rifles.
In a word, with these carbines you will find just about all combinations of barrel, chambering, backsight and reworking that the the Carcano family can provide! So please, dear readers, no comments about what is regarded as "correct" - it was wartime, and as must always be remembered, the arsenals were not producing weapons for collectors! The whole story is covered over 400 pages in a Germanbook, and this post is truly a very small extract from a very well researched work.
Finally, these carbines (at least over here) only fetch wallhanger prices, and putting it back into the original configuration is ACWOTAM - IMOH, of course.
Patrick