Hi Mathew. Thanks for your reply, it's much appreciated. The sherpa graph caseback is 34mm flat side to flat side or 34.7 corner to corner. I got mine off in the end by super glueing a 30mm nut to the case back and turning it with a spanner. That worked well and the glue dissolved in some acetone. It would be great to have the correct tool in future.
How much would you want for the opener .
Cheers
Mike
I'm in New Zealand for time ref
Unfortunately Mathew hunted high and low but couldn't find the caseback opener so I'm still looking. If you have one you're willing to sell please let me know. Cheers mike