early and late Tee Dee

Hello everyone,

how can one decide it's an early (~1961) or a later (~1980) Tee Dee .051 or .049 ? As far as I know the cylinder is different. There is a thin walled cylinder and a thicker, more rugged one, both .049 and .051. While  .049s have a #4 cylinder and .051s have a #5 cylinder. Moreover, the venturi mesh screen was added in around 1973.
That' s outside. Any clue?

Inside issues: when tinkering with .051 spare parts I found out there is certain parts that fit together and some don't. E.g. I have cranks that won't fit into cases and vice versa (cranks were a bit too short), some cranks have plastic washers, some have metal ones. Is there any indication which parts belong to earlier or later .051s ?

I searched the site (and the web) for these issues, but no answers so far.

Thanks
Roland

There was a change in crank and case, I don't know much more but this is a posting about it

https://www.coxengineforum.com/t1459-number-two-s