I've set up both three and four speed Osgears, and the fork for each type was the same. As Jan says, the only difference I could see was the number of holes in the lever.
Neil Foddering Weymouth, Dorset, England
> Date: Fri, 19 Mar 2010 10:01:15 -0700
> To: classicrendezvous@bikelist.org
> From: heine94@earthlink.net
> Subject: [CR] another Osgear/Super Champion question.
>
> >How can one tell if a Super Champion rear derailleur is for a 3
> >speed or 4 speed freewheel? Thanks for your help if you know the
> >answer. :-)
>
> The easiest way to tell is by looking at the indexing shift lever.
> The 3-speed version has 3 holes, the 4-speed version has 4 holes.
>
> From what I can tell, the actual shifter fork on the chainstays was
> the same for both versions. I compared the photos of the Oscar Egg in
> "The Competition Bicycle" with photos of a 4-speed. While it might
> make sense to have a longer shifter fork for more rear cogs, the two
> shifter forks look the same.
>
> Jan Heine
> Editor
> Bicycle Quarterly
> 2116 Western Ave.
> Seattle WA 98121
> http://www.vintagebicyclepress.com