You are looking at an Eagle Industries pouch hanger adapter in Coyote Brown. This MOLLE compatible pouch is very good used condition . It includes both the detachable top and the internal divider. This is part of the FSBE kit issued out to different elements of the USMC and has been used by UKSF. Please see pictures for more information. Label reads as follows:

8465-01-529-1612

8415-00-NSH-1138-KH

HORIZ POCKET ADAPT

W911QY-8-D-0011