Vintage Shimano 600 Rear Derailleur For My Bianchi

In building my vintage Bianchi Sprint, I wanted to stay as close as possible to the mechanical components that would have been used in the 1980s. But vintage Campagnolo components are very expensive. Beautiful, but expensive.
Instead, I got a set of early 1980s front and rear Shimano 600 derailleurs for a reasonable $54 on e-Bay. The vintage Shimano 600 rear derailleur may not have been found on Bianchis of the era, but they are age appropriate and true to the spirit of a vintage steel road bike.
Just for fun, I test fitted a new Tourney TX and a 1984 Alivio derailleur. While these could be made to work, they would not have been very attractive on this frame. So, I'm glad I went with the 600s.