I'm afraid I haven't got an electronic photo of one CK, but as I say the seat clamp is exactly the same as a 98 Merlin WCS that I have in this Total Bike test article that I have here, and the cable routing is exactly the same too. It had a Merlin decal on the down tube, nothing on the top tube and a Ritchey WCS sticker on the seat tube. I'm pretty sure Merlin marketed a WCS model for many years, starting from the early-mid 90s.
I'm afraid the format of the serial number doesn't ring a bell with me. It obviously raises the possibility that it's a 1997 frame, although that's as late as it gets for canti bridges. I wonder if Merlin themselves would recognise the format of the serial number as being from the maker they dealt with?
Am I right in thinking that the diamond shape of the drink cage bosses is quite distinctive? I'm sure I've seen that shape before, but I'm afraid I can't remember where.