I see what you mean, but if you look very closely, especially at the set immediately above the prop blade, you'll see there is lettering there. This was printed/stencilled onto the 'bar', which in this case is probably red, with black lettering, and was one of the alternative forms of presentation.
There were different forms of presentation, sometimes with the wording on 'bars' as in the pic, and more often, just the words. Much later, and seen on many airworthy Spits today, these bars/words wee replaced by a horizontal line and a vertical line, sort of I O -, which served the same purpose, one indicating the open position, the other closed, or locked, for the position of the locking stud.
I've got a close-up pic of the original style somewhere, hidden in my library, and one on a transparency from the work I did with the BBMF, but I think in the SAM Data File, and in the other colour book I sent, there's some shots showing the current form, as just described. It'll take ages to find the pic mentioned, as it could be in any one of around 25 or more books, but I can photograph the spinner of my 1/32nd scale MkXIV if it'll help, as the decals were included on the sheet for the Revell Mk22 I used as a donor kit.