A play that originated at Portland Stage Company in 2014 is a finalist for a prestigious national playwriting award. “Veils” by Tom Coash of Connecticut is among six in the running for American Theatre Critics Association’s New Play Award, which recognizes playwrights for the best scripts that premiered outside New York City. Portland Stage premiered the show a year ago. “This puts our theater in a different class of work,” Portland Stage executive and artistic director Anita Stewart said.