The valley effect on the lettering that makes it looks like two letters, in my opinion, is issues like
Die Deterioration and
Machine Doubling working together under improper lighting to make it look like there could be double lettering. If you look at the actual size of the devices themselves, the letters have actually been reduced and worn away, when with a doubled die, the devices appear larger than normal because the design is spread out. It helps to have a single angled light that you can adjust to highlight different high and low areas, which helps with having what Errers said, lighting induced doubling, and it will help you differentiate the types of doubling happening here.