There are similarities to Shanghai, and also, as Aidas says, the frame around the rangefinder window is not like the Shanghai (more like Zorki-3M, but with a recessed accessory shoe). So, given these unique features and differences, the way to tell for sure what the camera is, will probably be to look on the inside of the rangefinder housing, as well as other details of the interior and the outside of the rangefinder housing under magnification, to see what has either been done to the camera, or if it has a construction like a prototype.
It is harder to make fakes than it is to detect that they are fakes when the camera is in hand ... usually! As far as a "secret source" goes, I have found that it is good to look at everything that is presented ... many times the same source that has fakes also has some authentic rare cameras. For example, from one source, also in Moscow, I have been offered (several years ago) first, a FED No.194 (fake and I did not buy it), and second, a Zenit D Automat (perfect & working, which I did buy). Often sources are secondary and so are buying authentic cameras as well as fakes, both of which can be offered and who knows if the secondary source really knows that some are fakes .... probably, but maybe not! Here are both below:
http://www.ussrphoto.com/UserContent/fed4.jpg
http://www.ussrphoto.com/UserContent/fed2.jpg
http://www.ussrphoto.com/UserContent/zenitd1.jpgIn this case, I never had the FED in my hands and although somewhat obvious that it is fake, a more experienced friend helped me to decide that it was fake from the photos ... (and it would be quite hard to fake a Zenit-D, so that was an easy choice!).
Regards, Bill