I need some help for those that are good with parts numbers:

Looking to identify the part number and correct terminology to describe this part -- it's marked J121 and sits on a bracket attached to what I think is the Ignition Coil Assembly (Md131711). I always called it the ignition module but in my 89 raider parts manual I can only find reference to the assembly, same too with the FSM. I see this part (j121 thing) sold in lots of places but I'm not sure if there are different iterations of this same thing that need to be specified for my vehicle. Can anyone help me out? Many Thanks

EDIT TO ADD: It might also be called a power transistor