If you are lucky there might be a sticker with RM68090 or HX8347-G
But normally these Shields are a lottery. You don't know which controller is mounted until you run a suitable library and see what is reported by tft.readID()
Sometimes the pcb says 8347 or 68090 but this does not mean that it is true.
However these Shields are "readable". Which means that you can discover which controller ID is mounted.
Most Mega2560 Shields (with 2x18 header) are write-only. There is no way to identify the controller.
David.