I would not be so scathing, most transistors sold on Ebay/Aliexpress? are not fakes. Also bear in mind these dual gate FETs are static sensitive and may have been stored/handles incorrectly by previous warehouses/distributors, or even inadvertantly damaged by the purchaser without any knowlege. Dual gate FETs , even NOS are getting on in years, they are becoming a rare component these days.? Many sellers too, have no idea of what they are selling. The early 2/3 SK series dual gate FET lacked any internal gate protection diodes and were prone to gate "punch? through" by static voltages, the later types, the 40673 for example did have the protection diodes, and therefore more robust with handling.
