Ok Speedometer returned and money back.
I spoke with another refurbisher who wanted to provide me with a Smiths SC3304/11 but interestingly not the 1692 ratio. I think his book said S467/227/N but I cannot be certain so don't take my word on that. I do remember that he said the 1692 was not for the 16 inch wheel model. Now I am totally confused. HELP!!!!!
As these things cost an absolute fortune I really want to get it right this time! Does anyone have either access to the smiths books and could look up the info or upload the relevant page so I can see why he is telling me my 1961 3TA should have this other ratio drive?
I am so close to getting this bike back on the road - I just need to get a speedo and an MOT, so frustrating and want to do it this week if possible!