I bought quite a few items of Gibson clothes at Thomann. This T-shirt was one of them (I also got a beanie, a few baseball caps and a sweatshirt with a hood). The quality is probably not top-notch, but it looks fine and it will withstand a dozen of washing-machine cycles. After that it is likely to look crap.
The material is not exactly thick, just regular, and the neck opening is rather loose (IMHO). The Gibson logo is painted, not embroidered. It is made in what I may probably refer to as "cracked paint" style, maybe reminiscent of those vintage road-worn SGs and Les Pauls that everyone is hoping to find in their grand daddy's attick.
Definitely buy it if you are a Gibson fan.