I bought this camera brand new in 1996 from Samy's Camera in L.A. , and then paid Pentax Corp to modify it for long duration exposures with NO BATTERY REQUIRED. It can be used in the conventional manner with the battery, or a battery pack, but can be used for UNLIMITED time exposures as well. It has mirror lock-up in both modes. I believe it's the only one of its kind.
It is flawless, and already has a Beattie Intenscreen installed.
It's field of view (6cm x 7cm) has 5-10 times the area of the latest CCD chips.
$650 shipped and insured in the CONUS. US Postal m.o. or Paypal + 3%.