Its pretty easy to date the syncros cattleprod stem you own...
1990 : super-wide bar clamp (over 3"), and overbuilt (the 120 above is
290g).
1991 : Reduced bar-clamp width (just under 3") and some slimming of
material elsewhere reduced the weight of the stems to about
280g (the original weight for my 150).
1992 : A hole was added to the center of the bar-clamp for more
weight savings (now down to about 265g).
1993 : Switched to a Zicral stem bolt (with a finer thread pitch) in
place of the original steel expander bolts. Also deleted the
cable hangar under the stem. Drops ave. weight to 225g
1994 : Switched to a different color Z-Bolt (originals silver, new
ones satin-Ti colored) and added an extruded wedge with three
channels in it to reduce weight (down to about 220g now). First
appearance of the power-zit (a spot on the side where the weld
is built up - claims to strength the weld zone).
1995 : Same as '94 model year, isn't much left they can do to save more
weight except POSSIBLY thin down the aluminum some more (which
could be done if they switched from 6061-T6 to CU-92 to maintain
strength) and switched to Titanium bar-clamp binder bolts.
1996 : Cut away some of the material at the edges of the bar-clamp to
chop off maybe 5g more.