I had an inquiry about my 1966 Barth trailer and thought I would share this info with the site. The wheels are 15", 5 lug on 4 1/2" bolt circle. The hubcaps appear to be original and are 10 5/8" outside diameter and 2 7/8" deep at the center.

Thanks Mary
Mine are a 4 lug. I will take pictures & forward them.
Todd

There are two things that give a wheel its strength. The area around the bolts and where the wheel slides on the center hub. It should be a nice sliding fit on the center hub to ensure that the wheel stays truely concentric to the axle in the event the lug nuts come loose. In the pictures it looks like the wheel hub hole is larger than the hub itself. If this is the case, that could be disasterous.