I have the same unit on my CS30. They are certainly well built and long lasting. I believe it was made in Cornwall England
and may have been branded as a Merriman product. Mine is still working great but I was wondering were you ever able to get it serviced. The oil
refill hole is under the adjustment nut which unscrews after adjusting the roll pin to clear the arresting nut. This year I noticed a trace of oil
on the transom after unwittingly leaving the pressure on overnight. As such, I suspect that the seals
in the unit are due for replacement after 26 years!! Hence my interest whether you were able to source the seals as I am relatively nearby in Ottawa.