view door

When did EFM change the view door from round to square and why?

The door was changed during the years 79-81 for ease of working on the pot assembly burner plates.

Another question, I know the old boilers have fire tubes out the rear (very cool). Do the modern era boilers have the same design? If not when did they change?

I don't know when the change took place, probably 25 years ago, but the new DF models have a radiator style appearance.