Excursion jacket

An excursion jacket (or field jacket) has been part of official Starfleet uniforms at various times in the organization's history, most notably in the 23rd century. Designed to be worn on away missions, the jacket provided officers with more protection from the elements than the standard uniform.

Excursion jackets were in use in the 2250s, but fell into disuse in the next decade. They were again issued in the early 2270s, and continued into the 2280s, but again fell out of use sometime thereafter. 

Field jackets would not be issued by Starfleet again until the late 2370s. These were predominately dark gray or black, with division colors indicated by a sleeve stripe. 

Prior to the founding of the Federation, the Earth Starfleet also issued such jackets. (, et. al)