This JT uses a larger core that is typically found in low frequency applications such as EMI and RFI suppressors. This toroid has high permeability so it doesn’t take many turns to give a high inductance for a JT. The FT87-75 can be found at Surplus Sales for a dollar or so apiece.
The 2SC2500 transistor is a high gain, high current NPN, made for circuits such as a JT. The case is larger and it can handle more power, but the transistor doesn’t get warm.
