Austro Daimlers are kind of tough to pin down that way. There's a serial number registry at Classic Rendezvous, but I regard it as being somewhat unreliable. My impression is that it's a bunch of people who don't really know what year their bike was made telling you what their serial numbers are. It's either that or AD serial numbers were out of order, which seems very unlikely.

Based on a critical reading of the Classic Rendezvous registry, I'd guess that your bike is about a 1976 model. There's a guy with Vent Noir 5599620 who says he's the original owner and bought it in 1976. That seems like one of the more reliable data points. Some of the people in that list seem to have bought NOS bikes years after they were made.