(a) An indorsement may be in blank or special. An indorsement in blank includes an indorsement to bearer. A special indorsement specifies to whom a security is to be transferred or who has power to transfer it. A holder may convert a blank indorsement to a special indorsement.
(c) An indorsement, whether special or in blank, does not constitute a transfer until delivery of the certificate on which it appears or, if the indorsement is on a separate document, until delivery of both the document and the certificate.
(d) If a security certificate in registered form has been delivered to a purchaser without a necessary indorsement, the purchaser may become a protected purchaser only when the indorsement is supplied. However, against a transferor, a transfer is complete upon delivery and the purchaser has a specifically enforceable right to have any necessary indorsement supplied.