Ahh I see.. Well cant say for sure but LAPD for example uses "A" or Adam (from the phonetic alphabet) as a two man car or "L" Lincoln for a one man car.. sounds to me like that is what it is. Just my uneducated guess.
Two NH law enforcement agencies use(d) some of the "LA Police" style calling schemes for their units.
For many years Laconia Police used these style designators to identify units in the field. I haven't monitored them in some time, but they do not operate on the frequency you report. Laconia can be monitored on 155.790 with a NAC of 817.
Many years ago Rod Collins left Laconia and became Chief of the Newmarket Police Department. He instituted Laconia's system in Newmarket. A partial list is DAVID designated Detectives, ADAM designated administrative staff and PAUL stood for most patrol units. You can monitor Newmarket at 155.370 with a 460 NAC.
Finally, I have occasionally monitored some federal agencies using LA style designators on their spectrum in the range you monitored. You could possibly be hearing Border Patrol or Customs anywhere in that area of northern Vermont, New Hampshire or much of Maine with some units still utilizing that style designator. While many of their operations up there now encrypted, they still operate occasionally in the clear especially if operating with a local agency without encryption capability.