No text, but a visual code

[Linda]

To me the explanation is that the sign is an abbreviational x, together with the r, meaning radix, ie the middle letters are implied by the abbreviation. The timing might be taken as noon, seems reasonable, since any other time of day is more difficult to observe directly, but this does not mean the glyph means noon. Absence of any other glyph used with the r to mean radix of another timebase means you cannot show this one is noon and another stands for another time of day, therefore there is no evidence of any meaning other than radix, which can be any time of the author's choosing.

Plus the whole point of a radix is to be a root time to which you add or subtract the timing you are interested in. Why would you have two roots 12 hours apart? Just add 12 hours to the noon root.

It could be that evaK is really rx though, and even that it means radix. I had though of it as an rl ligature before, could be rx. 

I just dont think there is evidence for the noon idea. It also doesnt make sense to me that evaT would be noon and evaK would be midnight, the noon bit would still be there in the latter, wouldn't it? If anything evaT would be midnight, being a mirror of your noon glyph, if that is what it means. But then the r wouldnt be there to help remind it means radix. Or are you saying it means qx, does this abbreviation stand for something known?