Hi there, David,
I don't quite agree with Phil about the identity of your mini-mill. Yours certainly has a lot of the features of the Mark II like the motor enclosure and the integrated counter-shaft and back-gear. (It'd be nice if you could post another photo showing a side-on view of that back-gear please.)
However, on his 'lathes' web-site, Tony Griffiths says that the Mark II had graduated hand-wheels - your photos don't show them.
Your Z-axis handle looks like the one on my Mark I but with an added lever & knob. Also, your table appears to be turned end-for-end compared with mine.
Maybe your machine was a factory development model, a transition from the Mark I to the Mark II?
Your pix don't show the over-bar & outrigger bearing - do you have them?
How much have you used it?
Thank you very much for posting your pictures, I look forward to more discussion about both the Mark I and the Mark II mini mills.
There must be more of them 'out there'; come on, you guys, don't be shy!
Best regards,
Pete W.