The trucks outside of the building are Opel Blitz Trucks
Opel Blitz was the name given to various German light and middle-weight trucks built by Opel between 1930 and 1975. During the years preceding the Second World War Opel was Germany's largest truck producer.
The Blitz name (German for lightning) was first applied to an Opel truck in 1930 and by 1934 there were four base versions offered of the 1 tonne model along with fourteen versions of the larger 2/2½ tonne trucks. From 1939 onwards the 3-ton version was used frequently throughout World War II.