Vintage BMW Motorcycle Owners

I think it is for a sidecar,
I acquired a few motorcycles and some parts.
2 of the bikes have sidecars.
a 1968 R60/2 with a Steib S500
And
1972 R75/5 with a Steib TR500
Both sidecars are attached to the bikes. I see no place that this would go
2 ends have a small ball, kind of like a heim joint it's heavy steel.
Thanks for any help
Chuck

Hi Chuck-
The photo appears to show a subframe, for mounting a sidecar on a bike not already equipped with mounting points.
Your R75/5-TR500 rig must have a similar subframe, as no mounts were provided at the factory?
Best-
George

Thanks for the reply
There is no brackets on the 2 sidecar rigs I have. On both sidecar rigs the ball ends stay with the sidecar frame. kinda looks like a trailer ball and the threaded shank goes in a mount on the frame secured with a nut
One is a 68 r60 the other 72 r75 both steib's.
it must be from some other brand rig.