I just took a look at the Classic Rendezvous site's listed Austro Daimler Puch bikes and S/N's.

What I thought was a / on mine must be a 7 not stamped in fully.

That would make mine 6978460 best I can tell and there are 3 or 4 similar S/N's on that list apparently bought or had parts thought to be from 1981.

So, I'm thinking its a pretty good guess mine is a 1981 model. Whether 1981 or 1982 it's no big deal.

I noticed some of the older models had clamped TT cable guides.

Mine has brazed on cable guides plus the Puch head badge rather than an A/D headbadge.

As mentioned above mine also has Puch stamped at the top of the seat stays.

Austro Daimler serial number chart