Multiple graft counters may be placed on the same minion, but they have no additional effect. A minion with one or more graft counters gets -1 stealth, not -X stealth.
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Dr. Morrow, The Skindoctor
G5Sabbat: Morrow can put 1 graft counter on an ally as a Ⓓ action. An ally with any graft counters gets -1 stealth. Black Hand.
Rulings
Black Hand is not a title, it is a trait unrelated to any sect. The trait is not lost if the vampire changes sect.