Synchro?
Not sure why seller is calling them "Synchro" wheels, I have never heard that name in relation to Cromodoras on an X1/9.
IIRC the early years Corsa appearance package came with these wheels and I think here on Xweb that's what we call 'em, Corsa wheels.
I think the correct center cap is similar to the cap that came on the CD-58, except the Corsa center cap has a raised Bertone "b" on it. XWeb member "halojm" (Dave May) had them on his car at one time, they looked great:excited:
These are unique wheels, I don't think I have ever seen any wheels from any manufacturer that look like these.