marantz cd17 MKIII

Hi all, just wondered if anyone can advise if the top cover of these sould be screwed on or riveted I have two of these, one champagne and one in titanium and both have riveted top covers. I set these up with some of the other kit I recently inherited and they both give out a better quality of sound than the other players. Alas I don't have any remotes for these which is a bit of a pain but I will be keeping the champagne coloured version and one of the NAD amps. I was really wondering if my late uncle had had them modded (hence the question about the top covers). I put various discs through this and it seemed to get better the more I put through it. For such an old unit I am well impressed by them.

Cheers Mark :D