Do not know if it’s 100% fact but I think it’s safe to say they don’t ,
After googling a couple hundred images , none are graded by a real grading company - And there’s 82 listings on eBay , none of those are graded by a real grading company - couple encapsulated by something called SMA .
There is a Duke Snider graded by PRO .
https://www.ebay.com/itm/15556329314...Bk9SR9jykZXPZA