Back in the days
when manufacturers began making single-lens-reflex cameras, things
started happening fast. First the reflex system for small
cameras became popular. Immediately the concept of an
instant-return mirror came about. People wanted to hold the
camera right up to their eye, see the image the correct way around,
and soon enough, to have a built-in meter. These advances came
about in just a few years.
Many people buy cameras such as this
with a view to keeping them for some time. Manufacturers
realizing this created all manner of contraptions to extend the life
of these cameras, and of course to increase the number of ways to
utilize their manufacturing capability to generate revenue.
Which brings us to this item - the
Prism Finder. It looks positively silly but in actual practice
provides a good view of the viewfinder. It's a high-quality
item that judging from my example, would provide years of
trouble-free service. As we know, many manufacturers produced
cameras later with removable prism finders, with and without
built-in meters, and various capabilities. But this has to be
one of the earliest such devices intended for "old" SLR's.