A few months back CD-i member showed us a CD-i 452 player, which was in fact the same as a CD-i 450 player including the Digital Video Cartridge. It appears Philips did this to more CD-i models, as recently a CD-i 212 player popped up by member 'Treasure Gallerie': This CD-i 212 packaging is a regular CD-i 210 player, now already including the Digital Video Cartridge. Generally Philips sold the players without the cartridge installed, to keep the starting price lower but later on they included it to offer a more complete package. The language on the box shows this was a dutch unit (although we, based in The Netherlands, never observed it before) - I'm sure more CD-i units like a CD-i 222 or a CD-i 472 might exist as well.
[Thanks, Treasure Gallerie]