Under the proviso to Section 59 of the Negotiable Instruments Act, 1881, for a holder after maturity to…

The proviso to s.59 NI Act applies to a note or bill "made, drawn or accepted without consideration, for the purpose of enabling some party thereto to raise money thereon". Lack of a signature would mean there is no valid instrument at all, so it is the absence of consideration that makes it an accommodation instrument.