The Olympus 35 SPN from 1972 was an upgrade of the 35 SP. The SPN having an added battery check button and lamp on back as well as a couple of cosmetic changes.
This is a really good camera! an excellent lens. Either full manual exposure or automatic programmed exposure just dial in two A's on the lens barrel, focus and shoot. The camera has the option of normal (20 degree) averaging meter reading or with a press of the button (on the back) a 6 degree spot reading, just hold the shutter button halfway down to lock the metering and recompose and shoot! The metering works in all modes, it has the EV number displayed by the meter needle in the viewfinder, you can turn the aperture ring and/or the shutter speed ring to show the EV number on the lens (has a cutout section to the right of the shutter speed ring).

Fun with this camera.
Lots of dismantling and cleaning, stay tuned for more info.

Camera Specs.
Lens: 42mm f1.7, 7 element in 5 group construction. 49mm filter size.
Shutter: Seiko - FLA. Speeds from 1 - 1/500 sec + B.
Exposure meter: A CdS exposure meter on the camera body with average and spot readings. Powered by a 1.35v PX 626 mercury battery. (Which are unavailable now, I use a silver 1.5v S76).
Film speed index: ASA 25 - 800.
Viewfinder: Bright viewfinder, Double image superimposing system, coupled rangefinder. Marked with parallax correction marks. Meter needle read-out with EV scale along top
Flash Synchronization: Hot shoe and PC socket.
Self timer: On lens barrel.
Film Loading: Standard slotted take-up spool.
Film Winding: Single operation 120 degree winding lever type.
Size: 130mm x 80mm x 65mm.
Weight: 600 grams.