My Grandfather-What exact uniform is this?

This is my Grandfather Voldamars. Is anyone able to tell me anything about his uniform? We are Latvian and according to what I have been told, he was conscripted into the Red Army. I have an entire suitcase with old photos taken during WWII and prior. Many different uniforms are photographed. If anyone is interested in seeing them, I would be happy to share them.

The soldier shown is a junior non-commissioned officer of the Latvian Army prior to its incorporation into the Red Army (i.e. 1940) see http://uotw.heavenforum.org/t403-latvian-army-uniforms-1930-s
The badge just visible on his left chest pocket is that of his unit. I can't identify it for you at the moment, perhaps someone with better knowledge of the area can help.
Hope this helps.

Sean

Looks as if he were wearing the Army Staff Battalion badge (which means that he is not attached to this unit as his collar background colour would be white if it were the case). Pic from J. Vigups et al. Breast Badges of the Latvian Army, Riga, 2011.

I didn't get around to doing all of the changes made during the 1930's. The chart was just to give a general idea of the ranks for the 1930's
The dark background of the collar may be from an earlier period.
Here's a link from Luke off the Uniforminsignia site which may help.
http://translate.googleusercontent.com/translate_c?depth=1&hl=en&rurl=translate.google.com&sl=auto&tl=en&u=http://uniformologija.lv/raksts/karaspeku-veidu-krasu-atskiribas-latvijas-armija/&usg=ALkJrhhlQasYkT_fEmEI-YjKXZa3MLmOEg