Based on the chassis of the light special trailer A1 designed for the German Luftwaffe, different variants existed which were used especially on regular or field airfields. 

One specific sample was the type Sd.Ah. 25/4 (German Sd.Ah. 25/4 Nachschubanhänger auf Anhänger A1) also designated as supply trailer. It consisted of a simple cargo bed with closed top plate. Most likely it was used for transport of explosive or flammable material as fuel and ammo.