(a) General rule.--All letters of attorney authorizing acts relating to instruments or judgments may, if duly acknowledged, be filed in the office of the clerk of the court of common pleas of any county. Such filing shall be deemed a recording for the purposes of section 6106 (relating to certified exemplifications of records).

(b) Duration.--A letter of attorney shall remain in effect until a written revocation by the grantor thereof is filed in such office, but this subsection shall not prevent the prior termination by operation of law of the agency evidenced thereby.