Another Paglen classic, which I highly recommend to anyone interested in this sort of thing, is "I Could Tell You But Then You Would Have to Be Destroyed By Me: Emblems from the Pentagon's Black World".[1][2]

[1] - https://hatoffoil.files.wordpress.com/2016/04/i-could-tell-y...

[2] - https://www.amazon.com/Could-Tell-Then-Would-Destroyed/dp/19...

I Could Tell You But Then You Would Have To Be Destroyed By Me[0] is one of the books dedicated to these sorts of patches. My library still doesn't have a copy.

[0]https://www.amazon.com/Could-Tell-Then-Would-Destroyed/dp/19...

A nice book about patches from the "black world" of the US military:

http://www.amazon.com/Could-Tell-Then-Would-Destroyed/dp/193...

Some more memorable ones:

http://cl.ly/0p2g1H3y1p0P

http://cl.ly/473h003u0f0z

http://cl.ly/0M3h331s0d0j