W. Va. Code § 46-3-106: Unconditional promise or order.

(a) Except as provided in this section, for the purposes of section 3-104(a), 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 writing or (iii) that rights or obligations with respect to the promise or order are stated in another writing. A reference to another writing 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 writing 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 purpose of section 3-104(a).