Double Naught Spy
Sus Venator
Keep in mind the background of the author- he was a robbery detective. So his experience was in looking for criminals carrying guns in the role of an armed robber.
Okay, but keep in mind the purported utility of the graphic. It isn't about spotting armed robbers, none of which are depicted in the graphics. As noted above, all it shows mostly really are people who either aren't carrying properly or are just noobs.
The one shoulder holster tell is pretty good, only so few people wear shoulder holsters.