Hi Kevin,
The 3ttt Gran Prix stem with the recessed allen bolt came out about 1962-63. That early model has the word "Special" in a script font stamped across the front of the bar clamp. Those early stems also had an incorrect stamping on the side opposite the Gran Prix which read "Made in Jtaly." My 1962 Masi Special has this type of stem. When I picked up the bike, Faliero held up an allen wrench. When I gave him a perplexed look he pushed it into the stem hex fitting. Sometime in the mid-1960s the word "Special" no longer appeared across the bar clamp. But "Made in Jtaly" sometimes appeared. The words 3ttt and Special were now stamped vertically down the side of the stem portion that is inserted into the stirring column. The 3ttt with the Olympic rings is a 1970s version.
Michael Allison
New York, NY