Is this worth keeping?

[E. von Hoegh]

Coating, whether in the factory or privately done, is only on the air/glass surfaces. There are four of them on a Dagor, so it would be a relatively straghtforward job.

No it wouldn't. You have to unmount the lens - some were spun into the brass cells - uncement the cells, coat the two surfaces, and recement, then remount, the glass.