Shearwater information

I have acquired a “wooden” Shearwater 16.5 foot catamaran, that I wish to renovate. As it is “ALL WOOD”, I am assuming it is NOT a “Shearwater iii”? The “iii” model I am informed was wood/fibre glass (but as they were mainly built from kit form, I have to assume that my model mat be a model “iii”? I am struggling to find any information at all on the “i” oe the “ii” models? Is there anyone out there that could assist me with being able to date my version?
Thank you in advance.