LOLOL, film cameras, DSLR's, Canon focusing screens

I recently picked up an old 5D (full frame 35mm format DSLR) and liked it so much I spent 400 on a "refurb" 5DMkII from Japan which turned out to be just like new

I decided to research and see if any of the focusing screens out of my old autofocus EOS film bodies (That's FILM not DIGITAL) would interchange (they won't) but it turns out that ONLY TWO of the film bodies have the same style focus screens!!! All the others are different. I have 2--Elan-IIe (eye control), an Elan 7 and an Elan 7e, and an EOS 3. None of these were cheap in their day. The Elan's were sort of "semi pro" and the EOS3 was pretty much pro. Only thing "better" in that period was an EOS-1. Someplace around here I also have an EOS-M which "I think" was intended for students. I mounts the same EF lenses as the rest of these, but is all manual all the time. It does not auto focus.

ANYWAY it turns out from what I can gather that not only do the screens out of these film bodies NOT fit the 5D series, but evidently the two 5D's are different from each other!!

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