19 right. And I was in the Marines for 7 years. It's pretty sickening to think about how the lines are blended.
Most of it you can tell, like Zimobog said, by checking to see what their wearing and how their wearing it. Vehicle color is another. Black helmets are also a big give away for modern American warfighters. If it's plain, w/o a cover, they're going to be od green or coyote brown.
Two threw me still. The m60 and armored vehicle. Really, I knew the M60 was gone, except for certain sf type units, but really why would law enforcement need an M60?!
The other one with the Army DPU and the armored vehicle. Yes, the vehicle was shiny (not military) but they were all uniformly decked out in Army DPU.
I missed one that looked like a couple of soldiers in Afghanistan. Didn't see the black helmet.