Year?
Amazing.
Great fading on the fat font.
Serials go as early as 1.38m but most are 1.4-1.6m. Not common because they were a transitional dial -- they're from the same cliche that was used in the last gilt dial (before Singer settled on the Mark 1 cliche for the late 60's). They have the zinc sulfide puffy lume that has a tendency to crumble in spots. There was a nice one on eBay last year (should have bought it):
Beautiful zinc sulphide dial, that picture in sunlight shows it best.
I recently learned of the term “day glow” from a friend who I sought help on a 5513 I purchased that still glowed, as @michaelmc mentioned I initially feared it was relumed.
Here is my MK0 from 1967 1.4mil serial. Lume is white.