The Merlin serial number should be on one of the straps, embroidered, either on the underside, or inside the loop. It is unlikely that you would be able to see the serial number while the cover is still on the pool, unless you remove and inspect one strap at a time.  Here are some examples to show.  Please contact your representative with any questions, or if you haven’t spoken with anyone yet, contact us at 1-888-389-5065.  You can also email us HERE