MAC SSSW Stinger .22 Pen Gun Question

[msmp5]

Had an interesting question recently about my MAC SSSW Stinger .22 Pen Gun: “Why doesn’t it have the sear/safety pin?” Which made me wonder if that sear/safety pin was a modification or addition to the manufacture of these little guns at some point in their production run. (Mine does not have that pin.) Does anyone know the history of who made these, and when? Mine is a Powder Springs MAC which I got in 1991 and it was new - or so I was told (looked new) - when I bought it. Did another company take over making these from MAC in Powder Springs at some point? And maybe add the sear/safety pin later as a mod? Or is mine just missing it? I’ve looked at most of the stuff I could find about these guns via Googling, but if anyone else wants to provide additional info - specifically addressing this issue, or anything else relating to these weapons - it would be greatly appreciated. (The picture shows one of these with the sear/safety pin; mine does not have one.)