Genuine United States Marine Corps Fleet Marine Force (FMF) 13th Defense Battalion patch.

Good condition (see condition note).

Formed in 1942 during World War II as part of the Fleet Marine Force (FMF). Its original mission was to provide vital anti-aircraft and coastal defense for advanced naval bases. The unit served at Guantanamo Bay, Cuba, and in Hawaii before being officially decommissioned on September 7, 1944.

I am not a militaria expert -- I'm not not even an amateur. I am selling these patches after being given 400+ by a friend whose uncle collected them in the 1950s and 1960s. I have labeled them according to IDs via Google Images AI and similar online listings or quick references. I have judged authenticity according to common determinants such as material of the patch, style, backing, whether there are stitches, if it's still attached to fabric, apparent age, etc. If in my judgement, it doesn't look and feel authentic to the period, I am listing as either reproduction or unknown.