Milgauss blue parachrom hairspring

[Madprofx]

I have recently been looking at adding a Milgauss to the stable and was trying to establish with the 2007- models when was the blue parachrom hairsping introduced?
Was this something that was part of all 3131 Milgauss’ from the outset or was it added later in this era of the Milgauss?
Thank you all in advance


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