I own a DeRosa from about '76, I believe. There is no serial number or a tube decal and it has the NR/SR mix of components (alloy headset, lighter chain rings, two bolt seat post but with flutes). The lug's are the dubois, which have been built up with brass braze and filed smooth (the file marks are still visible). This bike is one of the cleanest bikes I have, at least to my novice eye, and I own a few nice bikes; an early 70's Ron Cooper, an '81 3Rensho, a late 70's Bruce Gordon, a 70's Sachs and an Assenmacher. Most of all the DeRosa rides very well and has never disappointed me, especially when I was tired at the end of the ride.
Brian Van Baush
Poulsbo, WA