Someone got this quill stem on these bars somehow. But I'll be darned if I can figure out where the sweet spot is to remove them.

As I recall the split in the stem has to line up somewhere key on the bar curve to allow it just to slip off. I thought it was to the inside of the curve, but it's getting jammed at every position I try it.

Any suggestions?

(though of course I could just keep and use them as a nice Cinelli set. but that would feel like failure.)

Pry it open a little?

Usually there will be a tapered section mear the bolt where the sides are cut away. That needs to be kept to the inside of the curve.

Your stem doesn't appear to have that cut, so odds are it depends on the stem being spread open (slightly) and oriented so the long dimension of the oval is radial to each curve.

Some stems used to have threads under the bolt head. You could unscrew the bolt, put a coin into the split and use the bolt (carefully) as an expander.

I have had stems with a little supplement bolt, beside the main binding bolt, that was clearly intended to expand the gap enough to facilitate removal.
There wasn't one obvious on this unit but, holy smokes. as I was reading your suggestions I backed off the bolt to see if - who know! - maybe there was some nifty reverse threading on the big bolt... But Now, it just came right out.

Only to reveal TaDa! a little bolt hidden inside the barrel of the larger bolt.
How cool is that! Those crazy Italians (this is ITM, who of course also made the insane seatpost clamp that had me baffled for a full year.)

Lesson? (there always seems to be a lesson.) When the answer seems reallllly complicated, (or when force seems necessary) it probably isn't.

Peter

it was somewhat seized but screwing down that inner bolt opened it up enough to slip off the bars.
FYI the gap had to be aligned with the outside of the curve of the bars.