Same as a YC-156, same as a 3CPX5000A. I tried to get the data sheet for the '179 from Eimac, they wouldn't do it. He told me it was the same as a YC-156 but tested to tighter tolerances.
I have a datasheet for the '156. If you need it let me know:
n2bc@stny.rr.com73, Bill N2BC