Speedmaster exhibition back question

[DJsub]

Hi,
I'm trying to further my education about Speedmaster exhibition back models, specifically models 3572.50 and 3573.50.
I'm aware of, and disinterested in, the debate regarding the difference in wording.
I'm more curious about whether both models always have the engraved words filled with a dullish black paint? I've seen examples where the words seemingly were not filled in but rather polished. I wonder if this minor detail might help date the watch?

Any one here have a thought or comment about this little bit of trivia?

Thanks and cheers!

[Kringkily]

They are enamel painted in the grooves. It wears off from polishing and usual wear.

[DJsub]

Thanks for the comment George.
Hope all is well with you after Hurricane Sandy and this week's surprising snow storm.
Cheers,