tag reads "Mark Man, CBS". Mark Man could be a sub-name or pseudo name for JM, while CBS most likely refers to a crew s/he is down with (hardly likely to be a shout-out to the broadcasting network....)
I'll be keeping an eye out for another lovely display of spectral spray from a paint can by JM on my visit to Baltimore this weekend - BELIEVE THAT!
p.s. take note of the "red flag, white X" posted on the vacant building in the backdrop. this is in reference to the failed conglomeration: KONY 2012