Here's a pic of a nifty detail on Caveman's little 50mm Nippon Kogaku. That's a reflex finder attached to the prism diagonal's eyepiece drawtube, same exact principle as the one built into the early Kodak box cameras.

I tried it out and it really works to get the scope sufficiently aimed, or before using the small finderscope for more precise aiming.

And that 18mm Nippon Kogaku eyepiece performed exceptionally well, as you'd expect.