OO-GUY
This aircraft might have been registered as OO-CUI as seen on this picture:
http://www.asa-be.com/images/PhotoGallery_BCR2/OO-GAA/OO-GUY.jpg
But the Belgian aircraft-register only mentions OO-FRE, registered from 1959-06-04 until 1970-12-01. Year built 1955
John