PSA/DNA
PSA/DNA is a third party authentication service that focuses on sports and music autographs. PSA/DNA uses synthetic DNA that is only visible with the aid of a laser to mark the item being authenticated. PSA/DNA also affixes a small sticker, which has a unique certification number, onto the item. This unique certification number matches a PSA/DNA certificate of authentication that is issued with the item at the time of the authentication.
LOA from PSA/DNA means Letter of Authority from PSA/DNA
Information courtesy of Heritage Auction Galleries