>>4036470It depends on the variant of 35mm you're talking about. One might get the f/2 version for better viewfinder illumination but that's moot when composing landscapes at infinity. As always non-MC marked, black-nose, ZUIKO models will have the most modern coatings.
The newer version of the f/2.8 is actually 70g heavier than that of the older one at 170g, I believe this reiteration started with the production of the black noses. I haven't found any additional information online but this might have incorporated an improved optical formula. None had aspherical or floating elements but are very lovely lenses to use with excellent sharpness and contrast. See this repository for serial numbers:
https://www.fredmiranda.com/forum/topic/1121708As for the camera body, it's just a light-tight box. All single-digit OM's have mirror lock-up save for the OM-2000 and maybe one more. You might want to entertain the OM-3/OM-3Ti/OM-4Ti for its zone metering feature, avoid the OM-4 for its rampant battery drain.
Lastly, you might want a larger format for landscape photography.