Can you diagnose this patchy look of the lens?

[seven]

coating issue, caused by ageing and some environmental factors like humidity perhaps. no fungus involved here.

[Mark Sawyer]

By the serial number, it's a late 1940s/early 1950s lens. Coatings of that time were softer and less well-bonded to the glass, so were more susceptible to mechanical and environmental damage. The internal coatings are more important for preventing internal reflections (which is where most flare comes from), and better protected, of course. From a practical standpoint, I wouldn't worry about it.

https://www.ground-glass.net/large-f...ock-lenses-age