The Cinelli headbadge on e-bay
looks to me not like a brass one, but one of the recent gold-plated ones. These were made for Cinelli for some "retro" or anniversary model. It's nice, but it's not the real thing. The actual badge (I have one, which Brian Baylis put on an old frame he restored for me) seems to be made from a very hard material, definetely not brass. Plus, it is a lot shinier than the old ones, and unlike brass, it hasn't lost its shine over the years.
I have notified the seller of my concern, and I am sure he/she will check and rectify, if necessary
Jan Heine, Seattle