Couldn't find any info on it, and it said Fluke, so I obviously had to buy it.
I guess its just a signal generator they built to easily demo their frequency counters.
...
Beautiful
I'd suggest that you contact Fluke to see if they are willing to provide any information. Guess that trying the phone number in the sticker is out of the question by now.
Seems that your photos could be a rarity to be found on the web, so... can we expect any "take it apart" in the mean time.
If any intervention was done over the years, some caps are gone by now. But if you intend to restore it, please take some photos before doing anything, just for history record purpose.
Glad you grab that piece of gear.