Very clean installation and an unbelievable presentation of the High-boy. I've never seen 'the case' in such fine condition, and someday you can take it to the 'Barrett-Jackson' Boiler Expo and come home with a 'First Prize!!'
I'm guessing that the capacity isn't even tested on a 20 below day, and that warm floors and no shaking a hand fed are benefits not even planned on. I wished you had the front cover off to show the Domestic coil mounted 'up-front' so that the rear clearance is not even an issue. FitzGibbons personnel may have done that modification without EFM approval, or why else was it not incorporated into all 520's. 700's,900's or 1300's that followed the 1954 end of the highboy?
You may have a new 'hobby' for the rest of your life!
There is no way EFM would of ever left one of their unit out of the factory not made under there specification.
Fitzgibbon made the boiler top to EFM specification .
I Think there are two reason why they only made the coil up front for 7 years is that when the coil is above the fire viewing door and the coil starts to leak you don't want water going into the fire chamber located In the back not a problem .
Two is appearance having two water lines coming out of the front does not look as good as having them in the back.
Remember back then they had full cabinet doors they wanted them to look like a piece of furniture it was the 50's look.
They made Highboy from 1948 to 1954 made a few units in 1955 .
First AP-1 520 came out in late 1950 early 1951 rear water coil .
First AP -1 350 1960 rear coil
First AP-1 700 in 1962 ended 1975 rear water coil
First AP-1 900 1965 to 1986 rear water coil
First AP-1 1300 1966 to 1986 rear water coil