Notes:

This is the earliest model I recall seeing of minisentry chan (September 2020), and is similar in design to the one by mochi, only much older by about two years (Mochi's minisentry chan was released on January 2022).
I'd call mochi a copy cat, but the design can be traced back to fizzywattr if I'm looking at the description of Mochi's sentry model on Garry's Mod right. The oldest gijinka of any of engineers sentries that I could find is a lolicon image of a level 2/3 sentry getting "sapped" by a blue spy, this image would later be redrawn by a different artist, this time featuring a rendition more similar to fizzywattr's design hosted on rule 34 paheal and rule34.xxx on 2020.