(more for those justtuning in, than you) - a learning lesson for the newer folks with the Federal interest(s)
a NAC alone does not ID an agency, nor does a Freq alone.
Now onto your find.
Remember - not all finds are shared into the RR DB for many reasons
Some personal, others tend to want to get, but not find/share
and for FEDS' over the years many of us, wanted to enjoy it among a close circle of hobbyists, so we have never submitted
plus as a Monitor, w/o insider information, you and others can only speculate on where the actual site is, which makes it hard to
enter into the RRDB and this is a good example as for you, on LI, it's not even in NY or NJ
170.5375 with $100 is likely (and with the RID, more than 95% likely) from over in CT
where ICE and HSI have a statewide Vote-Scan VHF network of 10 repeaters spread across the state, with two of their sites
located in NY (Hillsdale) and MA (Granville)
You are likely hearing the Betheny Repeater, next-time you hear that, search the 168-174 to see what other $100's you hear at the same time
I see this in the database on 170.5375 for other areas but not for NY area? there are many agencies listed
for NAC 100 but guessing it is ICE ...RID of 621xxx..73,s Marcy