The Masi with internal lugs was the 3V (or Tre Volumetrica), which originated in Italy and was made with oversized Excell tubing. Very innovative design and they are reputed to be great riders. After their introduction by Masi in Italy, some were made in California using a different tubeset (True Temper in at least some cases). The Russian 3Vs were California-built. 3Vs are cool bikes. Check eBay for value - they come up for sale fairly often. Neither super rare nor super collectible, except for the early Italian ones, which I think have a lot of upside. But definitely better and worth more than pseudo-Masis such as the Nuova Strada and Gran Corsa. Later (90's) there were so-called "Team 3V" frames built by Mondonico, which IMO have minimal collectibility relative to the earlier ones, but again probably ride nicely. These were originally built at the same time as the "better" 3Vs, leading to some confusion. Not long ago, you could still order a 3V to be made in California, and the Haro Masi folks have produced a replica 3V frame.
Do you have any more details or pics?
Also, could you please fix the spelling of Hetchins under your avatar, it's driving me nuts.