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What does the "19.01" mean?
(i.imgur.com)
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I'm not sure! If I had to hazard a guess, it would be that the board was assembled on Jan 2019. Or I guess 19th January, technically (although this seems less likely, it makes more sense to indicate the year I think).
It could also be the batch number or assembly line number, but it seems more likely to be a date.
The board version (V2.2) and some form of product identifier (DK001-D) already seem to be there, so those are ruled out.