I guess there where a few version of this joystick from Quickshot - for NES, Genesis and Multi-variant that has a switch (A,B,C,D) to make it compatible with the supported systems - A for Atari and so on.
I would like to use it for various Atari computers (2600, 800XL, 1040ST) and Amiga 1200. I guess that SIGMA is just re-badged but I'm not sure.