Wash. Rev. Code § 73.20.060
An affidavit, executed by the attorney-in-fact or agent, setting forth that the maker of the power of attorney is a member of the armed forces of the United States or within the class of persons described in RCW 73.20.050, and that he or she has not or had not, at the time of doing any act pursuant to the power of attorney, received actual knowledge or actual notice of the revocation or termination of the power of attorney, by death or otherwise, or notice of any facts indicating the same, shall, in the absence of fraud, be conclusive proof of the nonrevocation or nontermination of the power at such time. If the exercise of the power requires execution and delivery of any instrument which is recordable under the laws of this state, such affidavit shall likewise be recordable.
RCW 73.20.060