Easy!
The top cover and the top mounting eye both thread onto the damper rod (normal 8mm right hand thread). They are tightened together during assembly to act as a pair of locknuts. To dismantle, grip the top mounting eye in a vice, and "simply" turn the top cover to break the seal. If you are lucky (and the two parts haven't rusted together) you'l be able to turn the top cover by hand. If corrosion has got in, you could try using a strap wrench - but be careful as you could distort the cover. If that fails, (although I've not tried this myself) perhaps have a word with your local repair shop - there are tools around for loosening the seal holders on old-style telescopic forks, which might do the job without damage.
