Some Meritar flare:
I have to comment that the Cassaron is probably the worst M42 lens I have encountered -very flare prone despite the deeply recessed front element, and totally useless at f5.6 or larger because it loses all sharpness and contrast. Despite Steinheil's (recent) lofty reputation they did make some real stinkers.
The sun was just
outside of the frame -but I guess it reflected off the bottom of the mirror box and created this rather odd and distracting flare. Another reason to use a lens shade!
And of course a beautiful sun ring captured with a plastic "tiger boy" 110 camera: