It is most probably a Stoewer R 140 from 1933/1934. It looks like the pillarless fourdoor saloon introduced in February, 1933, which was built until the end of 1934 when a more streamlined body came out. It could be as well the R 150 from 1934 with a slightly stronger engine, as there were no external differences to the R 140.
The Stoewer R 180 had skirted fenders and a less curved bottomline of the windshield: