Feroze,
F magnifier was introduced for SF1/SFX cameras, FB magnifier was introduced afterwards I believe them to be identical.
The magnifiers that fit on the K-1000 are the older type. They work with KM, KX, K2, and the old Spotmatics. They are abundant on ebay.
I've used the FB magnifier and refconverter A or M on ME, ME Super, Super Program/Super A, and PZ-1/PZ-1p. The eyepieces are all identical mounts and they work fine.
The magnifier that fits the K-1000 doesn't work for the later cameras. The dimensions of the eyepiece are different, slightly smaller I think. Folks have talked about grinding a bit off of the mount on the old ones.
You can use on the news bodies (Z, MZ serie) older accessories (K, M serie): The width of the ocular is compatible, but small wings that enter in grooves of installation are merely too large. A good stroke of file is sufficient to adapt them: Attention:
- disassemble the claw beforehand not to damage the optic part.
- file what is necessary to keep compatibility with the old cases rightly
http://perso.wanadoo.fr/krg/Photo/bricolage.htm#Vis%E9e

