The box labels suggests it was a Italeri kit and Tamiya added figures which they have done with other manufacturers kits mostly for home market sales as imports are expensive as I recall.
Not that I know the differences but it seems both companies had M40/18 kits in the 70’s. The M42/75 seems to be a Italeri only plastic, with Tamiya adding figures and now Italeri adding a metal barrel with no figures.