Given that the RCD only became mandatory for boats delivered on or after the 16th June 1998, less than a quarter of all P275/P285s will ever have been subject to the RCD, been issued with a copy of the Certificate of Conformity, and physically CE marked.
Based solely on info in past sales adverts, #59 was a P275 built in 1997 [definitely pre RCD], whilst #61 was a P285 built in 1998 [month not stated] so this may help you to narrow the field of past or present owners whom you might approach for the answer to your question.
Geoff Sheddick
Parker 27/146 "Stroller'