Yep - I have one that is currently in my OM-4T. If I had more of them, they would be in my OM-2n and OM-2s as well, instead of the horizontal split image screens that are currently installed.Have you eve used one.?
I swear that in those other cameras I have to turn the camera 90 degrees in order to use the split image effectively at least 25% of the time.
I'd really like to have one for my Mamiya C330.