They built 785 M13/40s (?)
They built 895 M15/41s (?)
They built 112 M15/42s (?)
They built 467 Semovente de 75/18s
There were some other things showing up in late 1943 and through 1944.
Up to 121 of these with a 105mm gun were built. And some with 75mm guns.
About 100 of these were built.
Japanese tanks/SP guns with heavy guns were built in small numbers and not deployed outside of Japan
I misread, since those were the most common AFVs the Italians used on the Eastern Front. They did built a lot of the "M" (medium) tanks (the M13/14/15 types). Biggest negative with them is that they were obsolescent pretty much as soon as they entered service. Biggest positive is that most of them used diesel engines (not particularly powerful, but more flame resistant and forward thinking), and they did form the basis for potent SPGs and tank destroyers.
Also the Italians later SPGs/tank destroyers were widely used in southern Europe by the Germans and the RSI.
One of the more commonly used captired chassis the Germans used, was the PzKfw38(t) of Czech origin.
Aside from the tank itself, quite a few variants were based on the 38(t), the following being the more successful ones:
Sd.Kfz.138/1
Marder III
Flakpanzer 38
and most notably, the Jagdpanzer 38 aka Hetzer.
The 3.7cm Flak cannon went through several iterations between the late 30's and late-war 40's, being mounted on towed platforms as well as self-propelled, like on their half-tracks initially and later, medium tank chassis.