In article <4aimjr$doo@hobbes.cc.uga.edu>, tlister@sunchem.chem.uga.edu says...
>I recently purchased a Rolleicord III or IV ?? cheap at a photo swap.It
>is in great condition except for a cracked view screen which has been
>glued back together. I have read that newer Rollei models have Frensel
>screens to brighten the image, which for this camera is very dull,
>especially at the edges. I would like to replace it with a Frensel
>screen, does anyone know a good source? I am not interested in putting
>more than $40-50 in this. I did find frensel screens in an Edmund
>Scientific Catelog, 2.3" square for $16, but I don't have any idea
>whether they are appropriate for this use. Any help out there?

The Edmund Fresnel works fine dropped in on top of a plain ground
glass, but it does not have the texture necessary for focus if
it is used to replace the cracked screen. Edmund used to carry
a large Fresnel screen that incorporated a ground surface (though
it is not ideal for camera use, it is useable) - you could cut out a replacement screen from the center of one of these if they are still
available (scoring the plastic with repeated passes with a matte
knife, and then bending the sheet until it breaks, is a way to cut
the material).
Hope this helps.