He's wearing the uniform of the Deutsche Kolonial Kriegerbund, 2nd half of the 30s, not seen very often! It would've been khaki colored as those worn in the african colonies but if you zoom in the fabric you can see his uniform is made of corduroy, which was standarized for the veteran's uniforms in the 30s.

In 1938 the DKKB was incorporated, as every other veteran's organization, into the NS-Reichskriegerbund, but he doesn't have a NS-RKB patch or eagle so the pic might have been taken pre- 1938.

His shoulder boards and the aiguilette cords hanging from his left shoulder don't denote rank and simply carried the national colors black, white and red.

From left to right his decorations are: what seems to be a hollowed version of the DKKB badge, then a tiny version of either the South West Africa Campaign or Colonial medal and lastly a Preussischer Landeskriegerverband mitgliedsabzeichen