It's not a first run, as its has the more common longer reflector and head. it's a 16340 model, SST-50, running on a 1.4A driver.
I've not seen any pics of another, and have not found any references to engraving, other than the engraving Mac did on his Triple Triple MAG drop-ins.
It's interesting...I have to imagine Mac engraved it for some reason. It's a professional looking engraving and it begs the question...why would anyone engrave their light like that? That and the fact that he was known to do some engraving, which itself is a bit unusual. I wonder if it was a sample of some sort? The secret may rest with Mac ultimately, but my money says he did it. For what reason I do not know. Regardless...that is one fine light!!!