Before the Japanese Asahi Pentax S1a and SV, there was the German Practica IV F - a
wonderfully built SLR from Dresden. The IVF had a switchable lever underneath the mirror
which allowed the use of pre-set, or auto diaphragm, lenses (the screw mount M42).
The Meyer-Optik f3.5/30 is not the original lens. A silver 2.8/50 Tessar
came with my IVf in 1962 (or 1963?). Being an M42 screw mount body meant that after
my Pentax and Takumars arrived a few years after, they would also work. The downside
for the Practica was a non-return mirror, and quite dim focusing.

But I suspect it will last another 100 years.