Thanks for the update. Looking good and I'm pleased its functioning well for you.
I'm guessing that somewhere in its life, someone has replaced the motor with that from a Mark V, which would explain the off-white colour. Not sure why the heat tunnel is white though, never seen a National Machine with a square and white tunnel and the Mark V tunnel is tubular. Maybe someone just painted it white? (See photo of a Mark V, below.)
Looks to be in much the original condition that mine was in: The internal wiring is the same, fabric wound stuff and the heater and the way it's mounted is the same as well.
The difference - and I was expecting it - is the rheostat. Yours seems to have - what must be - a later modification, which changed the "flat-pack" style of fixed-resistances that mine had, with a more up-to-date (for the time) wire-wound and circular resistance. I think this is also why Lanzetter added the additional ON-OFF switch, as the circular rheostat did not have an OFF position, whereas the "flat-pack" version that my older one has, has the first stud-contact not connected to anything, thereby isolating the motor from the mains voltage when turned to off.
What's still the case, is that they were both just as unsafe really - even by standards back then - mainly due to the unprotected, mains-potential connections on the rheostat. It would have been a relatively simple thing to incorporate some form of protective cover over that area, to make it safer.
All the same, a good acquisition as it is and an even better one, once you have spent some time on it.
Good catch!
George.