Josef and the vintage BMW

Can you identify the model and year of this BMW?

During the holidays, we visited my mother-in-law back in Wisconsin. My wife, Mercedes, had been asking her to go through the boxes and boxes of old photos so we had some idea who the the people were in the pictures and where and when they were taken. Call it a little bit of family history.

One of the photos she had was this one. This is my late father-in-law, Josef. I never got the chance to meet him, but he sounded like a very neat man. Welder, fabricator, blacksmith, engineer, and car nut.

I believe this photo was taken in the 1950s in Austria or Germany. According to my mother-in-law, who is originally from Germany, the car belonged to one of Josef's friends and they had taken it on a trip.

Anyway, it's a cool old smaller vehicle. However, I don't know much about it. I'm almost 100% certain it's a BMW, and I believe it could be a 1936 315 or so.

Anyone know?