This appears to be the № 310 Mills revolver holster, found on Plate III
in a reprint of the Mills Woven Military Equipments. (See below)
I say 'appears to be' because the catalog does not seem to distinguish
between woven holsters for revolvers cal. .38LC (Long Colt), and those
for the .45LC model of 1909. This is the only holster represented for
use of revolvers; the other two displayed are for the pistol, model 1911
cal. .45 ACP.
In a prior post, I displayed a dark revolver belt, model of 1903, for
naval officers; included was a period photograph showing the belt
in use. Web equipment used by the Navy exist in relatively small
numbers because the sailors were not expected to constitute a large
portion of military force. Heavy losses from combat could cripple the
ability of capital ships to function; therefore, landing parties were
intended to be small, and the required gear to be limited in number.
Most of the fighting was to be left to Army and Marine forces with only
limited support from Naval landing forces.
Gear supplied to the Navy was small in number to begin with; the sea air
and salt water environment to which they were exposed likely increased
the rate of loss to wear-'n'-tear.
Although undated, this holster was likely produced in the 1909 - 1913
time frame. The production of M1911s didn't begin to hit their stride
until late 1912 when they began to replace in quantity older side arms,
which became secondary. Early holsters and 1903 revolver belts were
produced by Mills in khaki; by 1909 web equipment was produced in olive
drab. Appearing very much faded, this was originally olive drab.