Hi up for consideration is one used pair of KT 88 / 6550 by GEC England
Tests as 75% and 79% , one with a broken spiggot / base locator
what you are buying is one pair of tubes.
If you are interested in these ,I can attach a new locator on the broken tube if requested....see picture , it will reduce the pin length by 1mm
These tube had issues with breakages while trying to remove them , I have seen many broken pins on the KT88
thanks for looking.