Naa, it's factory lume mate, I have a ranchero exactly the same!
Not to cross swords because I seem to attract that lately, but mike said he's seen a few over the years and his collection is beyond belief. I'm just a lowly old watch collector who buys watches for watches, not for lume. If it is, it is, if it isn't then ok! I love this watch though! 😀
Not crossing swords at all, I believe it was added. I could be wrong, who knows. Sometime dealers added these at the time of purchase. It is a nice watch either way. You could always put a gieger counter on it, would at least tell you if it was old. 😉