Hello Adrian,  this is very interesting.

I assume that you find in the military notebook the Silintinsky's 41st Infantry Military Regiment.

It would be good to see a copy of that page with the name of the Regiment.

I know a very good book about this topic:  “Jews in the Russian Army, 1827-1917: Drafted into Modernity”, written by Yohanan Petrovsky-Shtern.  He did a lot of work in the archives of the Soviet Union, Poland, and gives information about sources in his book.  I know that there is a Military Archive in Moscow, which probably collected information.

https://journals.openedition.org/pipss/2313  - reference to Yohanan’s book

In our Bessarabia databases sometimes we have a records about retired military person, but most of the records are from 19 century.

Also it would interesting to know where your grandfather lived before going to the army?

Good luck to you with your research.

Yefim Kogan