I also use an old Kiev 45 degree finder from eBay on my 500CM. It works great for me, and although I periodically put the waist level finder on, I always seem to go back to the prism finder. Mine has a meter in it also, but I can't read cyrillic so I have no idea what battery it takes. And like another poster above, I'm a zone system shooter and always meter with my Pentax/Zone VI meter.