After a discussion with Vlad, I follow his advice and post some pictures of this Jupiter-8M lens I received few days ago (in fact, I received 2 of them). After comparaison (size, weight, image rendering, and visual comparaison), this Jupiter-8M is an Helios-103, I'm 100% sure about that. When you set diaphragme at f2, you are in fact at f1.8.
Now the question is what's happened in Arsenal so they did this?
Vlad already gave me a possible answer from his friend I. Zotikov, saying that they quickly planned production of new body Jupiter-8M, but they didn't had enough Jupiter-8M, so instead they put Helios-103 blocks in it (as far as I understood).
I'm curious to hear your opinion about this Jupiter-8M.