So far as I know, the Chain Banger stamp was a DTW custom stamp that wasn't really specific to the Birdie. I might be hallucinating, but I'm pretty sure I had an 86 Softie with that stamp.
The Birdie is one of those discs that nobody really throws or cares about, so the First Run Birdies with the rounded shoulder tops are kinda cool if you are a golf disc freak but they are not really worth anything. None of the old Birdies really are worth a lot other than the usual $20-$25 "collector" value for a mint one so far as I know. Thing pick up value when guys throw them. Markus Källström single-handedly created the market for old Piranhas because he made them throwers. Nobody throws old Birdies.