:spls:
Is that the remains of a felt pad on the bottom? Or of a paper label? And if it's the remains of a paper label - was it once white or did it have some sort of gold colouring?
If it's the remains of a white paper label, that could simply be the label that tells you not to put it in direct sunlight. If that's the case, it won't matter if you remove it to see if there's anything etched under it.