It would be a problem if you try to scrape it off and wind up breathing in a few dust specks of it and it gets into your lungs. It is not something to worry about very much so long as you do not disturb it and you keep it away from children. That would be a mixture of radium and zinc sulfide and even though is would not glow today, the radium would still be close to full strength since the half-life is around 1,600 years. The numbers on this one, and the hands as well, seem to have a luminous material on them which is the reason why the dial is black - so the numbers are more easily readable at night. Many military watches of WW1 had white dials also and conversely many civilian dials are found in black. Some American watch brands did not use a consistent series of serial numbers, but most of the big. In terms of a band, you can choose from Doxas characteristic Beads. The serial is always stamped on the outer side of the case back. In other words, 40XXXXX corresponds to 1940, and so on. The black dial (now faded to a brownish color?) is not indicative of military use. Not all vintage watches can be dated using the serial number. SERIAL NUMBER SYSTEM 1940-1966 In 1940, Doxa introduced a 7-digit serial number system, with the first two digits corresponding to the year of manufacture. I have a 1940s civilian wristwatch with a dial that is very similar for example. The dial seems to be more late teens to 1940s in style - it is hard to tell as this general style civilian dial was used for so many years. The overall style of the movement and the case do appear to be from the 1915 to 1920s range though. Doxa was not putting serial numbers on their movements at that time so dating such movements accurately is not possible so far as I know. The serial number of the case often is different from the serial number of the movement so going by that alone for a date is a bit soft.

Doxa serial number year