I'd agree its an amazing ride, stiff and fast and very responsive, its the over sized thin wall tubes mated to those special sleeved lugs that give it that feel, plus the short wheel base - work of art TBH!.
By the way I love the colour and how you've built it up very nice indeed. Have you had the frame resprayed?. How did you manage to fit a modern 11 speed cassette with the 126mm rear spacing? or did you have it widened?. I must say I've thought about putting a modern groupset on her as it would work so well, but in the end decided I'd leave her as she is to keep her in keeping with that era. TBH the old C-record groupset looks beautiful but just doesn't compare to modern kit. The gears especially are a pain to setup as are the Delta brakes.
Have you registered the frame on the Bob Hovey website (Masi expert)? if not contact Bob and he'll add yours onto the site. Looking at your frame it looks like an Italian built 3V. Also what is the code on the bottom bracket? You also may want to contact Alberto Masi to find out where it was built/type of tubing etc, just give him the codes from the bottom bracket. Good luck!http://bhovey.com/Masi/index.htmlhttp://bhovey.com/Masi/MasiItaly.htm
An interesting story about the 3V>http://bhovey.com/Masi/MasiArticles/MasiInterview.htm
Alberto Masi - firstname.lastname@example.org