Me and a friend took a 3 day trek up there from MD back in the early 90's....... My recollections are the old part Hartford was a paved over parking lot, we ran over to New London and dug a hole in a yard that was being renovated and did good. We found a stubby from Stoddard or Coventry a Dr Jaynes Vermifuge a pontiled mustard and a bunch of clay pipes etc. All and all the area wasn't attractive enough-digging wise- to justify a trip back. If you live in the area I suspect that a vigilant construction site monitoring program would yield a good find now and then!!!!Door knocking-permission asking- is always a good way, you'd be surprised how much interest is generated by a well spoken digger, especially if you appear to be doing research.....
ct - Keep your eye out for any Thames Glass Works(early glasshouse I believe in New London) - good stuff - if you find a threadless insulator from TGW,dont sell it for love or money.