You were right , it was old!
Basically made from '30 to '52, I believe. First five years were Oliver Hart Parr and had three speed boxes, I believe, along with the governor which was not as effective as the later ones, a different manifold with Kingston carb, and a few other minor differences. The mag was also different - a base fitted version, I think, and not so common these days.
Of course worth something, but often need extensive manifold repairs or replacement.
My first tractor was the one my Dad bought new in '48 and is still my favourite. Pulls like a train and starts reliably. Dropped a valve and seized - that ended it's working life, although by then it was far past regular-use on the farm. The governor had disintegrated during the '50s and was another weak area if not looked after.
I'm a fan of them and would like to think that even if not repairable there would be parts that could benefit other collectors.