Watch List notes:

USA, Connecticut cent, 1787, draped bust variety, large countermark "I. WALL" within crenelated rectangle, running from shoulder to top edge, obliterating the face, and causing a V-shape flaw on reverse and, seemingly, over a previous stamp ending in "S", stamp has caused curvature of flan, obverse very fine, reverse fine and with flaw
I. Wall is not listed by Brunk / Hallenbeck and the cataloguers can only speculate that he might be North American.

Estimate: 300 - 400 GBP