Parker 51 vacumatic restoration

[Bananabender]

Well the Parker Blue Diamond vacumatic finally arrived yesterday and I rushed into restoring it like a bull at a gate.
After a few spins through the ultrasonic and watching Grandma Pens UTubes on how to I tackled stripping it.
Not a problem except for one item , the damn cap jewel. I have tried heat , freezing to no avail so I’ll have to think about it a bit more.
What I know . The gold cap is 14c . The nib is dated 1943. The print on the barrel says ‘Parker 51 ‘ Made in USA , 4 . and after a thorough clean the pump works fine. In all my endeavours to take the cap jewel off I have lost part of the blue enamel so a bit more to do.