These are pictures of a Russian Ssh68 helmet.
The Russians call this helmet Stalshliem 68
Made in 3 sizes
The stamp in this helmet shows:
P-1 = POCT means size 1.
the 3ko is pointing to the manufacturer Zavod Krasnity Oktyabr (Factory Red October) located at Volgograd,
84 is the year of production 1984
Russian helmets compare
The Zavod Krasnity Oktyabr was completly destroid in the Batlle for Stalingrad.
In 1946 it was rebuild.
The company still exists, my Russian isn't that good: http://www.vmzko.ru/