These trucks were produced by Strombecker. As you can see they were produced in several different sizes. From left to right they measure 7″, 6″, 5″ and 4″ long. The 7″ Supply Co. truck is the only one of that size that I have seen. The 6″ truck is the same as a 5″ truck but an inch longer due to it being a trailer.
From my private collection.