Space Age Electronics AV32-WHEN?

Does anyone know when Space Age Electronics first put out their combination stobe/horn units, like the AV-32?

I’m not sure exactly, though I think visual signals first started being required sometime in the 50s or 60s. Also the AV32 & its variants are just light/strobe plates, that’s it. A separate audible signal like a horn is meant to be mounted behind them.

I’ve got a few in my collection that are dated March 1980, but I think they date back to at least the mid 70’s.

Thank you for the info.
Are you aware of anyone who has any of these for sale?
any condition.

I’ve got a few spare complete units, and some modified plates, PM me if you’re interested.