(1)Where a simple signature on a blank . . . F4 paper is delivered by the signer in order that it may be converted into a bill, it operates as a prima facie authority to fill it up as a complete bill for any amount . . . F4, using the signature for that of the drawer, or the acceptor, or an indorser; and, in like manner, when a bill is wanting in any material particular, the person in possession of it has a prima facie authority to fill up the omission in any way he thinks fit.
