I think I have some original Sharpes thread at home from when I used to build for Somers before Jim Somers died. i will have a look this week.
Remember, on all Sharpes rods used with a fixed spool reel, the bottom most whipping was copper thread.
I have a very rare Sharpes "The Carp" at home that you can have a look at if you would like to get the butt 100% correct/genuine.