If it's the stove with three windows then it's probably the VF8-ST8. I have one of these stoves and the dist fan is, I think, an original. The label reads as follows:
No. 7021-1835 Type U21 RPM 2860
V 115 Hz 60 A 1.1 HP 1/30
Model 50752-D500 CFM 135
I played around with a slightly larger fan and it didn't seem to make much of a difference, but it wasn't that much more powerful.
If that is in fact the right stove, I have a manual for it if he needs one.
Let me know if I can help in any way.