It has been ridden hard and put away wet and as far as I can tell from the Ruger site, this old girl was built in 1973 and was the last of the old models.
Serial No is 32-057XX
It is on sale for $AU450. Ruger Blachawks new are $AU925 from the big gunstore interstate and around $AU1100 elsewhere.
Here it is:
I always fancied getting one of these and converting it to 44Special. Foolishness I suppose, I'd be better off buying a new Blackhawk in 44Special, but I've never had a custom gun.