In construction, a 3:1 fill slope (3' horz. for every 1' vert.) is alot different than a 1:3 slope (quite steep).
So I would expect a gear ratio to be assumed to be front/rear, never thought it would be taken otherwise.
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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"