Many years ago I made a small batch of mainshaft tools to lend out to others in the series community.
Part number 600-300. They where free to use but inspite of asking for a returnable £20 deposit not all came back.
Having a bit of a clearout I have two left, they are made from EN24T steel with 1/2" square drive and 30mm hexagon. (Not to be confused with the Chinese ebay offerings) for sale at £15 each posted. PM if interested.
Age and health mean I will never run another series so maybe help someone.