PJ Production from Belgium makes resin aftermarket accessories for aircraft, as well as some very nice resin aircraft kits. Among their many products is a series of ejection seats to replace the usually plain kit-provided examples.
This particular seat is a Martin Baker Mark 4 seat. The listing isn’t more specific than that, but says it is to be used in Lightnings, Alpha Jets, Canberras, Hunters, and Vampires.
Now, I’m not entirely up on the Mk 4, but I know that most of those jets used different versions of the Mk 4, along with seats other than the Mk 4, in various versions of the aircraft. For instance, the Lightning used Mk 4BSB, 4BSC, 4BST, etc., while the Canberra used the Mk 1C, 3CSB, 4Q, 4QS, and others in various versions of the aircraft. I’m pretty sure the differences in the different types of Mk 4 were visually minor, so that’s acceptable to me.