De rosa Concept - TT -bike. On seat tube is written ALUMINIO, but the frame is from steel. I was very surprised about that. The front fork is from carbon fiber. The frame seems to be built in 90s, but I didn't find any information about it. I found few Derosa concept bikes, but all of them were aluminium frames. On the rear brake bridge is little hearth and on the rear drop-outs is a engraved DeRosa. Very nice find.