I still have one of those but I'm not sure where it is... probably in a massive junk pile of electronics gear in the basement. It was just a basic freq counter -- I think 25-2GHZ or something like that but it did work OK. I'm pretty sure mine was from Optoelectronics.
I remember these being quite hot back in the late 90s... but wasn't there a fancy version where it detected the "mode" of the RF signal as well? I swore I saw one of these... it had one of the first LCD displays (on a freq counter) and it told you everything from the CTCCS tone, DPL, RF signal strength and I thought the very last version told you the mode as well... like AM, NFM, FM, WFM...
I'm still doing research but here's one company that is still around:
http://www.startekvideo.com/FREQ%20CTRS.htmPrices aren't cheap and nowadays, you can use CloseCall or SignalStalker just as easy.
Here's an interesting option:
https://www.amazon.com/Surecom-SF401-PL ... B01AOTJH6Y