The Velocity stem is an interesting topic. As Pip says, it was the same from the Lava Dome upwards. The P2 fork, however, was only triple butted for the Cindercone model and upwards presumably because of completing price point and to make distinction in the ranges? Having owned both, there is a big difference in frame weight & feel in performance between a CC and a Lava Dome.
91' range aside, for the Velocity Stem in 1993, there was also a polished silver Cromoly version that made it's way onto the Hot which is quite rare (See US catalogue) As above, the design for the 93' stem was considerably lighter than the 91/92 ranges, in continuation of the 'Racelight' brand theme and integrated cut-outs.
Following a tip from Raiden73, I replaced the steel M5 quill bolt of the Velocity Stem with a titanium version to shave off a chunk of weight (I'm not frequently downhilling it at the weekend
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There is also a 120 or 125mm length version, making the 4th variant, but unsure of the rise without measuring.