A common problem I've noticed on old LEDs is that the maker's name that is etched into the glass and filled with white paint is prone to wear off.
This was the case on this Beltime that I bought recently:
So I had a go at repairing it. I used a water based white paint that came out of a Revell model kit. I overpainted not only the letters, but also the immediate surrounding area - mainly because I didn't have a fine enough brush or a steady enough hand! I let it dry for a few minutes, then scraped off the excess paint using my fingernail. The paint wasn't entirely solid, but was hard enough to unstick from the smooth main part of the face, leaving the bits in the indented lettering intact.
Here are the results:
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