solved 6745 Please me identify this part?

I am replacing a cylinder head gasket and somewhere in the process of removing the head I had a small part drop to the ground and I cannot figure out where it belongs. It looks like a cap/seat of some description. Maybe sits on the end of a rod but I am not sure if or which. Photos are below. It was coated in engine oil so I believe had to come from somewhere around/in the head. I feel really stupid about this one sorry. thanks for any help.

This is a valve stem cap as used on the old 8mm intake valves on the older cylinder heads in the UR1 from 2011 to 6748.

parts number 95 0533

Zetor 4911 to 6945 and newer doesnt have this anymore...

Thankyou so much. I have a workshop manual file but the exploded diagrams are all blurry and all the small parts look the same.