IVU in oval is the marking of the Fourth Technical Control Unit (UT) of the Regio Esercito. When the factory came under German control, the marking changed to 4UT, but it meant the same thing.
Love the little Berettas! Here's mine, a minty 1941 M1934 in 9mm corto. It is Italian army marked. The gray-green leather holster is the same as yours, late war, made by the Italians but used by Germany as well. It was the same good quality leather used in other WWII Italian field gear.
How the gun's finishes changed in three years!
These pistols were very popular as pocket pistols with GIs on passes and leaves because they were hard hitting, reliable, and easily concealed.