Welcome. I'm thinking that actually it may be a little later. I'm not sure where fiddlebase got their info. It looks like most of the machines that are seen on that link up to 1890 have a fiddlebase bed rather than the rectangular bed. There is another page that may or may not be helpful at
https://www.naehmaschinenverzeichnis...inen/gritzner/ There are some other links for Gritzner at
Gritzner treadle sewing machine
If all the parts are there, I would clean it up with sewing machine oil, and then oil the places that should move and sew with it. I would love to have a transverse shuttle machine to sew with, especially if it had been my grandmother's.
It is hard to tell how many collectors are in Russia and if there is much value there. It can be made to look a lot better and probably sew, but a lot of people do not have the time, patience and knowledge to do it by themselves.