I dunno - I haven't ever had a UGC-129 - but the capabilities look similar.
The UGC-129 manual I found on line is an Air Force TO but has what looks like a 1977 Navy contract number - weird
TRACOR, INC. N00038-77-C-0077
Did the Navy fly them aboard P-3 Orions?
Probably the Navy needed something that was gray and twice as heavy for ship/sub ballast?
The military era between mechanical machines (Model 28, Kleinschmidt) and PC/LCD seems awful schizophrenic to me.
Lots of versions with essentially the same features.
Huh - I found this in a 1986 DCA report on UHF SATCOM -
"A prevailing problem is the teletype ASCII character length where the Navy uses 7-bit and the Air Force uses 8-bit"