DVD set ratings password bypass

If one purchases a used DVD player from the second owner and there is no way to reach the first owner and one wishes to set the "ratings" back to #8, not knowing the first owner's password, how does one reset the player back to factory defaults or whatever? The manual does not even address this issue not does the manual advise how to reset back to factory defaults.

Is there any widely-used trick, such as pushing and holding PLAY and STOP simultaneously or whatever?

The transport mechanism in question is a Matsushita/Panasonic DVD-A11OU/CA.

Thank you!
I would look inside the unit and see if they use a battery to store this info. If so, I would remove the battery and let it sit for a while, and then try it.
Thank you for the good suggestion - but there is no such battery. I have another unit with a tiny pin-hole in the front panel that you poke with a sharp pencil point or whatever in case of a reset emergency. Oh well . . .
Try steps 4 and 5 of this procedure.

-- Al
Thanks, Al !
I will not be able to try this until Monday - but I will post here regarding whether or not it worked on my particular unit.
Cheers !
Hi Al --
It worked!
Just to share the information: You push and hold Rewind (skip back) Pause and Eject simultaneously and the unit will reinitialize. I had to hold the buttons for about 30 seconds before it reacted.
Well done, Al - many thanks!!