I stayed in a Sentry Motel in Gretna, LA in early 1970. Gretna is just across the Greater New Orleans Bridge, and the motel was located on the Westbank Expressway, just up the street from the Sentinel Motel and the Gaslight Motel.

A Google search indicates that it's still there. It doesn't indicate a chain, like the plural "motels" in the ashtray, and Google doesn't find a chain.

The logo looks vaguely familiar, but it's been a long time. Maybe the tray's from there, maybe it's from some defunct chain somewhere else