HYA3696 is the part number for the Cooper S and Clubman GT boot board. It is an Australian part (identified by the Y in the prefix) so would've helped Leyland comply with the local content government legislation in place at the time. You'll see it says Parts & Accessories so your board was sold as a spare part. The original must've gone missing or been damaged so required replacement at some stage. Regardless it is exactly the same part that was fitted on the production line.
Haven't seen that label before. Nice score.
