In an O.Henry story about actors:
"One afternoon Bob Hart presented his solvent, serious, well-known vaudevillian face at the box-office window of a rival attraction and got his d. h. coupon for an orchestra seat. "

What in hell is a "d. h. coupon"?

Something to do with professional courtesy, I'd imagine, although what the d and the h stand for, ya got me.

Dear consuelo: the only thing I could think of was "deadhead", which I have seen referring to a wagon
or train, or car part of the train, being carried without
any payload. It seemed to much of a stretch to apply that
to getting free admission to theatre.

The h might stand for honorary, but I'm still scratching my head about the d meownsef.

Deadhead: one who follows the Grateful Dead on tour