I think I figured the meaning of the LPS-GJ. It was so obvious that I did not stumble over it.
Following the Russian system the projectile type (here LPS) is given followed by the case material. In Russia that would be (in correct English transliteration) LPS-GZh.
Transliteration from Cyrillic into Latin alphabet languages is different from country to country as it depends much on the pronounciation of the Latin letter in every language.
Means a transliteration to English is different from one to German or to Romanian - as we see here.
So the Cyrillic “ГЖ” is the Romanian “GJ” and the English “GZh”. All this is denoting a cladded or galvanized steel case.
AIRcarbine, it would be great if you could pull one of the cartridges and show us the separated projectile and tell the OAL of it. The weight should be at 9.7 gram.