Sorry it took this long to follow up. First and foremost, Thanks for the replies to my post. I asked Tiffen if they always mark their filters and they said yes. So I notified the seller and informed him that there was no Tiffen ID markings. He kindly gave me a refund and said that I could keep the filter. I was still curious... and I finally got the chance to do a quick test with the filter today, see attached photo. Top image has the filter and bottom one is without.