I like it, nice shot. Good to see that he's exhibiting proper safety by keeping finger outside the trigger guard
The "POW 4" could very well just be a label put on the weapons assigned to whatever unit he's in, we did similar things with the weapons owned by our squadron in the USAF in Korea. Much easier to keep track of at a glance than the serial numbers...
Wish I had a chance to try out an MP5, I've heard they are a lot of fun to shoot. They're sure out of my personal budget reach, though!
Jim