Part 3 - Installing replacement parts and reassembly.
Internally, the transformer core and mechanism were in good condition.
Replacement parts are:
The original handwheel was black plastic, but had a large crack right through it, so a metal one was fitted instead.
The hole on the top was probably for a switch of some kind, however no switch was present when the unit was obtained.
The spindle of the new rotary switch fits through the same hole, and fixes with 4 small screws for which new holes were drilled.
The switch is a 3 pole type, but only 2 poles are used in this application.
Electrical connections are made via a 13A plug and a trailing socket - originally there was a 13A socket mounted on the side of the case, but this was very old and unsightly.