That GMT looks fantastic with the brown dial!

I am a designer.. and in printing we use a mixture of 4 colors to create a deep black.
Same goes for dial printing as far as i know... to create deep black you don't just print 100% black.. as that would be pale.
You use a mixture of colors that add up to a deep full black. SOmetimes ending towards blue or warmer versions.

As far as i know.. the dialprinters changed some of the mixtures in the 60th.

You see it with Speedmasters.. etc.
And for sure with Rolex. Late 67-70 dials have the tendency to 'change' to brown.
Mk2 and MK 3 Seadwellers and mtr's first Redsub's...

But also late 60'th Gmt's and 5513's do so .. but rarely.

As if other pigments fade in the mixture and the warmer, more red pigments become dominant.
On the MK2 Seadwellers.. it's almost harder to find a black one then a brown one.

Keep them coming...