[SOLVED] Rear wheel «spacer/collar» removal help!

Hi
I recently purchased an old 1982 honda CB400n in quite good condition, except the rear wheel, or rim I should say. The seller provided a replacment rim, but it is sadly not the same as the one on the bike. (Different colour and size? See pictures)

so the rear wheel was not broken per say, as it was in daily use when I bought it, until…! I hit a pothole and everything came loose. After closer inspection, it seems as the collar or spacing which ties the rear sprocket and chuson pads togherer as broken :-(

I am now trying to reuse the collar from the replacment rim, but it seems as it might be stuck, or not supposed to be removed.

Is there anyone in this forum, who has removed or had this problem, which knows what to do? :-O Are mye only options a new rim? Or could I salvage the parts from my replacement rim?

this is the replacement rim.


and this is the original rim.

the damage.


collar part from replacement rim.
Exploded view of replacement rim, I pressume.

thanks in advance for all help! And please excuse my poor english, as it is not my native language.

Happy riding, best regards CB400norway :-D