If that flip is real, some scammer will buy that just for the flip, find an uncracked slab, insert a counterfeit Mantle and you'll see it back on eBay.
Collecting 1965 Topps High #'s SGC 88 or better: 10/91
BUYING Well Centered:
1956 Topps SGC 84 or Better (or raw equivalent)
1965 Topps SGC 88 or Better (or raw equivalent)