Old Boston place called Caverly's Diner.
Fried smelts, awesome. Looks like it might be near North Station (with the overhead T line etc). Can't find a trace of it on the internets besides reference to a LIFE story though. Again, the below from the
LIFE photo archive.

The Calvery (sic) Diner.
Location: Boston, MA, US
Date taken: 1971
Photographer: Yale Joel

Wide angle view of customers eating at the long counter in the Caverly Diner. [note Miller High Life box propping up the donuts in foreground, sweet]
Location: Boston, MA, US
Date taken: April 1971
Photographer: Yale Joel

Fried smelts sea food dinner, a specialty at the Caverly Diner.
Location: Boston, MA, US
Date taken: 1971
Photographer: Yale Joel