I am visiting my parents this weekend. I will get the number of the machine shop then.
Here is a view of the top plate from below. The hole in the center is that which the bolt goes through into the EQ6 Pro. The ring of holes are threaded and allen bolts screw into these to hold the head of the mount down.
-------------------- Orion Optics UK 350mm Dob
Celestron 8SE
Bressier R-127L + minus violet filter(F=1200mm achromatic)
ETX125
Revelation 80mmED
W0 ZS66
EQ6 Pro
DSI I