There were two versions in service when the war began; the earlier one is distinguished by the absence of a driver's seat and wooden hubs. (Some of these were later updated with steel wheel hubs.
The later, and more numerous version was the Feldbckerei M1901. It had a full driver's seat, and the steel hubs. Arie, a member of this forum, has an excellent drawing of the former vehicle I've described.
As information, this was a Korp vehicle, with some 25 supplied to each Korp. Each wagen could produce 1,600 loaves per day.
Matador and MGM both have different models in 1/72 scale of two types of Feldbackofens. Furthermore, MGM also has a model of a Teigknetwagen (dough kneeding machine). Figures can be obtained from Munich kits, who have two sets of German bakers.