I got one last year. They are nice.
They are for the MG3 which means it can run a MG42.
There have been modifications done to these mounts to run HK, but that was a lot of work to lift the mounting points. I think one company actually makes a adapter to run the HK.
I run a MG34 (with an TGW adapter) on it. Works great. Very happy with it. I need to look up the instructions how to properly use it. So far I've only aimed and pulled the lever. Note that to make the trigger work, I reversed the finger and added some hard foam to get it into the right position to pull the trigger.
Later I'll 3d print a real part or 3d print an sleeve adapter.
Yours look like it is slightly better condition.. The guy who owned it before didn't collapse the front leg and it ripped the padding just in the middle, sides look great. I wish I could find a replacement. Otherwise some military OD green duck tape is going to cover it up. Wanna sell/trade+cash your panel?