I count 39 victory marks. On Thursday, 5 February 1941 claimed his 40th victory(a Hurricane over
Desvres,
France). Could be a photo taken because of this victory, him being the 4th highest scoring LW ace.
III,/JG3 was based at Desvres from 8.8.40 - 16.2.41
http://en.wikipedia.org/wiki/Walter_Oesau
http://www.ww2.dk/air/jagd/jg3.htm