Hello to all,I need some help with some needed info.I have an old HS TARM oil and wood boiler.The only information i see on it is the date of 3/27/1978.I need to find out a model number atleast. I think it's either an OT-35 or an OT-50?All I could find is a spec sheet with the dimension listings,(neither of them seem to be an exact match?) Any help is much appreciated!