Saw this somewhat rare (to me anyway) Dale Brown (CRlistmeister) track bike at Hearn's Cyclery in Asheville a few weeks ago:
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1989 Schwinn Paramount OS
1980 Mclean/Silk Hope Sport Touring
1983 Bianchi pista
1976 Fuji Feather track
1979 raleigh track
"I've consulted my sources and I'm pretty sure your derailleur does not exist"