You say the estate was settled, so I would guess the will was probated because that is the only way there would actually BE an executor. I know in PA unclaimed property is classified as less than $500 or more than $500 so figure out if its worth the trouble. If you are not the executor, no you could not obtain a short certificate, because a short certificate is like an ID card for the executor - who is not you. You can find out who the executor is and ask him/her to claim the property.
If his will was not probated then you might be able to file a petition to determine heirship which would award the property to his heirs at law. In any event, you should consult PA counsel to determine whether the time has run for a "short certificate" or "small estate" as we say here.
Legal disclaimer: Donald J. Quinn II is a Missouri attorney. As such, his responses to posted inquiries, such as the one above, are limited to his understanding of law in the jurisdiction in which he practices and not to any other jurisdiction. In addition, no response to any posted inquiry should be deemed to constitute legal advice, nor to constitute the existence of an attorney/client or other contractual or fiduciary relationship, inasmuch as legal advice can only be provided in circumstances in which the attorney is able to ask questions of the person seeking legal advice and to thus gather appropriate information