Reclaiming an old Master Cylinder

After successfully resurrecting two old Lockheed callipers which had been knocking around in the shed for 25 years, I turned my attention to a RD250LC Master cylinder.
It’s possibly 35 years since this one has had any attention.

It had the normal seized and rounded 4mm crosshead in the top which I dealt with in the time honoured manner of dremmeling a slot across it for use with an impact driver. 
An hour of heat and hammers later, I finally beat it, and opened it up.

I’m sure that’ll clean up all right!