There are a steady stream of posts on the Forum about whether a particular early Soviet watch is 'good' or 'bad'. Here is some advice that can help you minimize costly buying mistakes, from someone who has learned the hard way.
A wise man once said...
"Knowledge is knowing what you know. Wisdom is knowing what you don't know."
When considering an old Soviet watch, be honest with yourself about whether you have the knowledge required to determine if it is authentic. If you don't, seek help.
True, there aren't many good books on early Soviet watches out there, but there are plenty of web resources around for you to consult when you aren't sure if the watch you are considering is authentic. Among others, the site maintained by ill-phil is quite extensive and has many good photos of pieces that are authentic.
My site is also quite comprehensive, with more 600 different watches and clocks illustrated -- many of them early pieces, which are my main interest. My site also has a search function which has pre-defined searches by date, type, and for many 'brands'. You can also do a custom search for any word or number.
There is a sticky in the 'Articles' section at the top of the Russian Forum page that offers a very extensive list of other sites that can be of help to you in one way or another. USE THESE RESOURCES. They will keep you from wasting money and, ultimately, they will help you build a collection of Soviet watches you can be proud of.