J W Benson Age

Hi
Just hoping to pick some brains - these watches seem to be a bit of a minefield due to the Benson - Smiths association!
So J W Benson Tropical with, I believe, later 'non Dennison' case, 16j movement and larger marked sub-seconds. Any idea
of dates - maybe late 50's? I have had a new mainspring fitted and now running well. The case is in excellent condition - no
sign of wear, just a few marks to the rear from clumsy opening or not as the case maybe.

Any thoughts gratefully received.

Yes, late 50ies, with radium.....

What is the obscured number beginning C4xxxxx near the balance? That will give you a year of mvt manufacture +/- 1 year, it's likely 1958/9.