Forgetting the lack of lume and the markers with black inserts for a moment, that dial does look to have original scripting to me and even the little offsets on the numbers in the register. Which begs the question about the grey register.

From it's first appearance as cover model on the '72 brochure:

through '74:

this is shown as having a white register. The catalogues aren't a huge help really - as I found during my Carrera research, they only give the base colour of the dial with no mention of register colour, even when it contrasts.

This one puts me in mind of the register on a 1553 N, as that's not white, but it is a metallic silver finish rather than the apparently flat grey of this one. To me, it looks almost like a layer of primer to which the white paint has never been applied... though why would you then go on to apply the numbers in the register.

Heuer had a number of problems with the blue paint on the dials in this period, particularly for the photosensitivity that sees it fade to a number of different shades, including some lovely violets. Looking closely, you can see a number of slightly different finishes on both Carreras and Monacos from this period, as the paint mix was being tweaked. But I've not seen any problem with the register paint before, or with the blue paint bleeding onto the register, so this grey one has me pretty much stumped. Anyone else ever seen a grey register on these?