Joest & Kremer where allowed by Porsche to make a couple of replica 936's. To get round the fact that Porsche did not want to be seen selling 936's the 2 teams had to call them 908/80's.
The photo is of the Joest car from 1981 at Le mans. This is the same car that Mass crashed at Silverstone in 81 and Ickx shared with Joest at Le Mans in 80 that came home 2nd.
The factory relented and both cars ended up with proper 936 chassis numbers (.936/80-004).