We always stop at D’Amato’s deli in Portland (on the way to Tenants Harbor) every summer - just to buy their heroes for supper. They claim to have invented it.
I grew up in Maine and all my extended family still live there, but I've only been back a dozen times in the last thirty years. Whenever I'm there, I always have to get an Italian sandwich from D'Amato's. I used to drive a delivery truck down route 1, stopping in every little coast town. Camden is by far the most quintessential Maine town. Go to Camden if you have a chance.
Amatos deli. They are in several towns on the coast of Maine. Personally, I think thier Italians sandwiches are expensive.
I live in Portland. There are lots of good restaurants both in Portland and Old Orchard Beach. Just pick what feels right. You will probably find me at Pats Pizza at 30 Market Street when the Red Sox are playing.