[The Philpott]

Lovely. I am going to take a punt at 1960-1964. It seemed to me there is a lot less data around concerning old 'Record' equipment than there is for old 'Megger' equipment.
When i was tackling a 500v hand cranked Record insulation tester i had to wing it, there didn't appear to be anyone current on the forum who had dismantled/serviced one. Ultimately a bit disappointing as it would only push out 50v and a very tiny current sub 1mA- shorted turns presumably.

I would estimate that what you have there is quite rare.

Dave