Assigning ownership to a marker so it can't be flipped

Ok I have some generic markers that need to be hidden with a question mark but only revealed by the player who brought them on the map.

Process is player A brings on map, flips them sets them up to start game. I only want the player who brought the unit on to be able to flip them back to reveal the minefield etc.

I tried a Mask but the who can flip seems to be useless in this case since it is a generic counter.

Can I set the who can flip to a the contents of the variable $PlayerSide$ instead of putting text in?

CAn I assign a marker to $Playerside$ also?

If not how else can I do this short of creating the markers are part of that sides counters?

I haven’t tested this but you should be able to use the Restricted Access trait, using the tick box for the player who deploys