Sylvania SDVD 6655 -B
May also be sold under Curtis brand (untested on Curtis brand).
Switch player on
Press eject on the remote to open tray
On the remote, press 9,9,9,9 then 0
Region:0 should appear on the screen
Switch player off, then on again
Should now be multi-region
This is a Philips hack and may work on other Sylvania models