[Hallicrafters] HP 5300B measuring system question

[Waldo Magnuson]

Does anyone have a manual for the HP 5300B measuring system and if you 
do could you look up and tell me if accepts a 10 mHZ external input to 
lock into.  The HP 5300B is sensitive enough to measure what I want to 
but my HP 5328A counter isn't sensitive enough although it does have a 
ext. freq. input.  I'm trying to make some long-term frequency drift 
measurements.  I can borrow a rubidium beam standard if my HP 5300B 
will accept it.
Thanks for the help.
73,  Skip  W7WGM