This machine is a copy of the Singer 45 (may be the Shuttle barrel is a little different???) It was built in the USSR about 70s-90s in the former Singer factory before the revolution.
It is class 23. You can Google https://www.google.ru/search?q=пмз+23&newwindow=1&client=opera&source=lnms&sa=X&ved=0ahUKEwjG5427idjYAhVISZoKHbBpDrcQ_AUICSgA&biw=1024&bih=711&dpr=1.25
Class "23" is written here.