The label on this trailer says it is a Sporty, yet the person who owned it advertised it as and Alder. The snaps around the trailer, show that a cover was a part of the trailer. Unable to tell if the frame and the body are steel or aluminum. If you have any info on this brand of trailer, feel free to drop me a line and tell more.
UPDATE:
I recently acquired a Coffman Single
Wheel trailer that I am restoring and while working on the site I noticed that
this Alder trailer has the same frame and wheel assembly as the
Coffman trailer. Take a look for yourself. 