Numbers, Numbers, and more Numbers

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Pardon a question that may seem quite obvious to most, but after much time searching the forum, the stories, and the net, I can’t cypher anything. What do the numbers preceding a watch and caliber mean? For example from a recent post on a watch recommended: “Quite a nice 166.010 Seamaster Cal 565 in steel in the UK”.

What does the 166.010 actually mean? They are used ubiquitously and I realize they denote an immediate image to most of you, but I can find no reference to them so that I might get on the same page. Is there a comprehensive list that I’m missing? Are those numbers connected to calibers? Is an understanding of them crucial to expanding my knowledge of Omegas?

Quite amateur questions, I’m sure. I’m at a loss nonetheless. Can someone point me in the right direction?
 
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In the particular example you quoted, 166.010 is the case reference number.

1 = Gents Watch
6 = Self-winding centre second
6 = Water-resistant Calendar
.
010 = 10th iteration of the series describing the case/bracelet style