The rest isnt stamped?
No combination of the HIN info you provided comes.back as a valid HIN at either site I use to decode HINs.
HinDecoder.com
Are you in the US? Never heard of Derben, which is an Australian manufacturer. So probably in Australia, correct?
The TWA at the beginning of the HIN you provided comes back to
TIEDE & SONS FBGLS CO
Which was based in El Paso Texas, and was only in business June 1981 ro April 1982.
Pix might help, but as an apparently American made boat, in Australia, w an invalid HIN, its going to be tough to ID, IMO.
Check and make sure you've posted the HIN correctly.
Having Au- at the beginning, and ag2 stamped at the end, it would seem that it has a state (or government) issued HIN that wont decode to provide a year, except perhaps to the year the HiN was issued, rather then to the year of the boat.
Dont know for sure, but the HIN site I posted above, has an Australian 'version'
http://www.hindecoder.com/index.php?...alia-Boat-Code
And heres where I looked up TWA
https://boatdb.net/manufacturer/tied...gls-co-TWA.htm
Good luck
In Australia, boats arent titled or registered? Doesnt that paperwork list a year?