M.P. 40.27
The Gold Collar Mine was located on the north side of
Prosser Gulch about 100 yards above the Gilpin main line.
One of the questions about the Gold Collar was how the
Gilpin serviced it. In Gilpin Railroad Station Listing by Dan
Abbott, Mr. Abbot says:
M.P. 40.27
Gold Collar Mine Spur
The Gold Collar Mine was located on the north side of
Prosser Gulch just above its junction with Eureka Gulch. This
180-foot spur for the Gold Collar mining and Milling Company was completed
and ready for use on March 26, 1910. The entire cost of this spur -
$289 - was borne by the Gilpin Railroad Company and hte track was the
property of the railroad company. This spur was build to provide
a loading point for the Gold Collar Mine and to better facilitate handling
ore for the Castro Mill. Construction began March 23, 1910 and was
completed three days later.
However, if one goes out to the track roadbed of the Grand
Army and keeps walking out past the Grand Army into Prosser Gulch, one find
a roadbed that extends all the way to the Gold Collar. The
screen shot below shows the trackage based on this roadbed.

The question is, when did this trackage exist and for how
long?