Dextell (a.k.a. Nice Ideas) was an offshoot of the French branch of Mattel's Intellivision software house. Full details about Dextell / Nice Ideas are at the Intellivision Lives! site.

All the copies of these overlays that I've seen are the papery style, just like some of the later ones made by Intellivision, Inc.

Note: Unless otherwise indicated, images shown are from overlays in my personal collection.

If you find a version of an overlay does not appear on this site, please report it!