The postcard appears to be from the Munich House of Art series. A nice period piece displaying an MG unit in close combat. Photograph seems fine at first glance too. A useful thread can be found here on the forum, which offers many tipy and hints for what to look for when authenticating period paper items. It can be found in the Photos - Paper - Propaganda forum.
Currently working on several KZ related projects, including items for the USHMM, Groß-Rosen Museum and various private concerns and studies. Available as a guide to KZ sites, contact for details.
"maka akaŋl oyate maŋi pi ki le, tuweŋi wíyópeya oki hi sni"