I don't think that was EVER a Harford County frequency. Are you sure that's not a typo?
FCC Licenses for 453.725 in the State of MD
Licensee Frequency Callsign City County Svc
CHARLES COUNTY, MD 453.72500000 KXE563 LA PLANTA CHARLES PW
OAKLAND, CITY OF 453.72500000 WNUK770 OAKLAND GARRETT PW
MARYLAND, STATE OF 453.72500000 WRB476 COLLEGE PARK PRINCE GEORGE'S PW
It was never lisc by Harford Co because of it being Low Power use for simplex comms between haz-mat techs while on scene wearing level A suits.
Also I pulled that frequency from a Haz-Mat Portable with a freq counter as well as the other two frequencies that were in the portable, but I did not post them. Need to know basis and at the time no one needed to know.
If you read in Police Call, in the beginning of the book and the FCC website for Low Power comms and surveilance, agencies dont have to have a lisc, however the stipulations are they cannot cause interference with another user on that frequency that is Lisc.
That is the reasoning why no one can find MDE's Frequencies cause they are not lisc by MDE and are low power for simplex ops between MDE Personnel for on scene comms.
Guys believe me there are lots of low power comms goin on out there that people just dont know about cause they are blind and oblivious to it cause if it's not listed or lisc it just cant be so. Open your eyes folks.
Checking some old notes, and you're right.
The HT1000 portables that Hazmat team members carried had
Channel 7 453.725 with a tone of 136.5 running full power (5 watts)
Channel 8 455.850 same tone and power
Channel 9 459.125 same tone and power
They've switched over to the 800 Mhz system now, so I'd be surprised to hear any comms on these channels.