The tank badges are glued on. However, there are threaded holes underneath once you remove them. Looks like Triumph originally planned on using bolt-on badges.
I've had an issue with one of these threaded holes, where it may be just close enough to the inside surface to allow some gas vapor to seep through. This caused the paint to raise around that area. It took months for this to happen though. I had it repaired once, but it did it again later. My painter has since passed on.. So, the second time, I cut the bubble off, and covered it with one of those bullet stickers... and it's been that way ever since. The bullet sticker has stayed well and actually looks kind of cool, so I've just left it at that.
You can see the sticker in the pic below, about where the H would be on the Triumph emblem.