That looks to me like a British 'double adult' motorcycle sidecar, like the examples below.
In the 1950 and 60s, a whole family could travel in/on a motorcycle outfit like this - possibly including not only 'the wife', but 'the wife's mother' as well...
Being a British sidecar, it would only have a door on the left, so when this (German?) Isetta owner wanted to use it, it was mounted backwards so that its door is now on the right.
These sidecars are excellent examples of ultra-light monocoque/unibody construction and the fact they are still around show how a well-built lightweight body can last.