Cannondale identification please

Once A Hero

Senior Retro Guru
Latest on this;
I had to cut the plastic end caps off of the skewers so that I could get to a metal part I could actually grip with pliers. Both skewers now removed (and subsequently knackered).
Stem bolt undone, and the wedge nut moves up and down in the steerer tube - but the stem won’t come out of the steerer. I managed to move it about a 8th turn one way, but now can’t move it back!
The whole headset/stem/steerer has been soaking in Plusgas for a few days, and this evening I was able to rotate the forks almost fully - so at least the Plusgas has freed up the headset bearings.
I can’t get the wedge nut out of the bottom of the forks as there is a rivnut of some sort for a reflector or canti-stop mount, so that’s limiting my ability to work on the stem from below.
Plusgas applied where possible for the time being!