Okla. Stat. tit. 12A, § 12A-3-106: Unconditional Promise or Order

UNCONDITIONAL PROMISE OR ORDER

(a) Except as provided in this section, for the purposes of

subsection (a) of Section 3-104 of this title, a promise or order is

unconditional unless it states (i) an express condition to payment,

(ii) that the promise or order is subject to or governed by another

record, or (iii) that rights or obligations with respect to the

promise or order are stated in another record. A reference to

another record does not of itself make the promise or order

conditional.

(b) A promise or order is not made conditional (i) by a

reference to another record for a statement of rights with respect

to collateral, prepayment, or acceleration, or (ii) because payment

is limited to resort to a particular fund or source.

(c) If a promise or order requires, as a condition to payment,

a countersignature by a person whose specimen signature appears on

the promise or order, the condition does not make the promise or

order conditional for the purposes of subsection (a) of Section 3-

104 of this title. If the person whose specimen signature appears

on an instrument fails to countersign the instrument, the failure to

countersign is a defense to the obligation of the issuer, but the

failure does not prevent a transferee of the instrument from

becoming a holder of the instrument.

(d) If a promise or order at the time it is issued or first

comes into possession of a holder contains a statement, required by

applicable statutory or administrative law, to the effect that the

rights of a holder or transferee are subject to claims or defenses

that the issuer could assert against the original payee, the promise

or order is not thereby made conditional for the purposes of

subsection (a) of Section 3-104 of this title; but if the promise or

order is an instrument, there cannot be a holder in due course of

the instrument.