Posted By:
MarkI don't have any great advice on this, as some come right off and others are tricky. For the tricky ones, the residue left behind can be worse than the ugly sticker itself.
All I can recommend is to gently work on one edge of the sticker with your fingernail or a tweazers. If it appears to be coming off clean, then gently and slowly keep removing it (little by little). Don't rip it off like a Band-Aid!
If you are getting any resistance, stop at the very first hint of it, and just press the sticker back on. I personally think it is better to mat over the sticker, than to permanently scar the piece with sticky/gummy residue.
PSA and/or Spence will surely be able to advise you best on this... I would call them before attempting.