Can you help to identify these frames, bikes or parts?

I just bought this bike today, looks wonderful but according to the columbus sticker the frame's been repainted.

The frame was built in Rotterdam by Cees Jonkers. I believe the tubing to be columbus (fork crown), but maybe you guys could help me find out what tubing (sticker doesn't specify this).

Some photo's... If you'd like any more photo's that could help you I'm happy to provide.

Thanks a lot!

Looks very similar to my 'rider' frame, certainly the same lugs, bb-shell and rear bridge, mine is Oria tubing, very different forks but i wouldn't recognise those as being columbus.

Are the dropouts stamped?