[Whewt22]

There's a few things hinting apon this such as the charm, but that's really a stretch.
Considering Isshin could of realized Ichigo wouldn't just wear a charm if he gave him one. But saying it was once his mothers, in turn made him wear it, thus preventing Kon form spirit based attacks. Or it really could just be his mothers, and that would mean shes knowledgeable of shinigami and hollows thus having somekind of powers.