Hi Leon
A partial answer for the 500mm Mk II can be found here:
https://www.imaging-resource.com/len...ii-usm/review/
Quote:
"The lens comes equipped with a rotating tripod mount, which features click-stops at ninety degree positions. The lens includes two tripod feet: a larger tripod foot with 1/4'' and 3/8'' size sockets, and a smaller foot that can replace the larger foot for use with monopods, with only a single 1/4'' socket."
Cheers
Dennis
EDIT:
There is a lo res 3rd party replacement drawing here:
https://www.hejnarphotostore.com/pro...-asterisk-.htm
But it may not match the Canon OEM foot?
EDIT #2:
Hi Res Hejnar replacement foot drawing here - scroll down the page.
https://www.scvphotoideas.com/2013/0...-canon-ef.html
Cheers
Dennis