I never know where or when I will find something unusual or interesting, something I've never seen before... like a one wheel trailer. They are in demand by VW people I was told by this new owner, he'd just got if off ebay
That the wood and plate are in such amazing great original condition is astonishing, the major frame piece has been repainted, but the wood wasn't touched
The reason this doesn't fall over (like a person on a unicycle) is the from cross member that is bracing the side to side load ( it's the black part at the bottom of the photo below
The advert is from a JC Whitney like catalog that Randy let me scan, Warshawsky's http://justacarguy.blogspot.com/search/label/Warshawsky