Okla. Stat. tit. 12A, § 12A-3-308

PROOF OF SIGNATURES AND STATUS AS HOLDER IN DUE COURSE

(a) In an action with respect to an instrument, the

authenticity of, and authority to make, each signature on the

instrument is admitted unless specifically denied in the pleadings.

If the validity of a signature is denied in the pleadings, the

burden of establishing validity is on the person claiming validity,

but the signature is presumed to be authentic and authorized unless

the action is to enforce the liability of the purported signer and

the signer is dead or incompetent at the time of trial of the issue

of validity of the signature. If an action to enforce the

instrument is brought against a person as the undisclosed principal

of a person who signed the instrument as a party to the instrument,

the plaintiff has the burden of establishing that the defendant is

liable on the instrument as a represented person under subsection

(a) of Section 65 of this act.

(b) If the validity of signatures is admitted or proved and

there is compliance with subsection (a) of this section, a plaintiff

producing the instrument is entitled to payment if the plaintiff

proves entitlement to enforce the instrument under Section 52 of

this act, unless the defendant proves a defense or claim in

recoupment. If a defense or claim in recoupment is proved, the

right to payment of the plaintiff is subject to the defense or

claim, except to the extent the plaintiff proves that the plaintiff

has rights of a holder in due course which are not subject to the

defense or claim.