Sweet example of a 51 there Gil.
It amazes me the subtle differences among all the original 27 examples of the 51...little things like water fittings, built in pulley on the governor base, hour meter, water height gauge, boiler feed tube from water pump etc. (or not) etc. I suppose as each was built over time, the availability of components was a factor and/or simple improvements in available parts and pieces. I love it!
Rog