Im sure many agree, the best part of collecting is to be able to study subtle differences.
Here is another look at the recession on the earlier dial, as I have not found many if any pictures showing the glare reflecting this way to capture the action.

Questions:
-Did they use this dial version only on all of the early productions until a certain point?
-Did they use the flat dial to cut cost, or get a different shade of blue?
-Are there lighter blue dials with flat registers, or darker blues with recessed registers?

Comments:
Flat dial has bolder font and hashes, smaller lume dots where the recessed dial has bolder register font and top heavy 5's

Note: Excuse, the glare on the crystal as it captures light when trying to achieve this, also if this has already been discussed or shouldn't be discussed.

Many thanks,
Mike