Originally posted by ChrisPlatt Nikon Photomic "heads" show the set shutter speed (F) or shutter speed and aperture (F2) in the viewfinder,
so even if the exposure meter is non-functional IMO they're a better option than a plain prism - which shows neither.
True they are larger and not as cool looking, but they're available at a fraction of the cost.
I think it's a collector thing, more than outright usability. A dead meter prism is a blight on an otherwise working camera. And parts haven't been available for a long time. There were rumours (or just hopes) in the late '90s that some shop in China or India might consider tooling up to make replacements to keep Nikon Photomics going, but digital came along too quickly and ruined that party.
While a dead meter prism still has its shutter and aperture displays (depending on the model) it's still a shadow of its former self. Putting a prism on that never had a meter is technically less useful (no displays, just a focusing screen inside) but it is neat, tidy, and functions as fully as it was intended. To the collector/user, unbroken beats broken any day.
And then again, you've got a good excuse to dig out that hand-held meter and take incident readings of everything - which beats built-in meters most days of the week.