TCVB Tokyo Convention & Visitors Bureau."
At least I think it's a hachimaki -- based on this Wikipedia description, which explains that in Japanese culture this kind of stylized headband is "worn as a symbol of perseverance, effort, and/or courage."
It was tied on to my head in just the manner pictured above by my travel section compatriot who described its provenance as having come "from from the JNTO (Japanese National Tourist Organization)."
To which I say: ありがとう
(which I'm really hoping means "arigatō" or "thank you" in Japanese.)