My understanding of the subject:

Mills had a patented process for weaving the cartridge loops into the main belt. The ends of the belt have a well marked riveted brass-fitting. The fitting has a heavy hinged open "C", which hooks onto the belt for adjustment.

Competitors - Hurlburt, Spaulding, and Russell & Gilbert Loom received SAW contracts, but, sewed the cartridge loops onto the main belt.

Spaulding belts are very light weight canvass and the ends have a light leather binding, (not riveted fittings).

Hurlburt belts are heavy (like Mills).
They have three woven stripes, which I have a hunch may have aided sewing on the loops.
The Hurlburt belt-ends have a riveted brass-fitting, but, it is different from the Mills fitting.
The Hurlburt fittings lack patent markings. They have a light brass-wire 'bail', that encircles the belt and when adjusted is concealed between cartridge loops.

I am unfamiliar with the Russell & Gilbert Loom belt.

Note - It is not unusual to see Khaki belts that were dyed Blue for some type of later service. They often have faded to a blue/gray color.

Attachments: 1. Mills woven loops.  2. Detail of Jason's Hurlburt (50 loop) belt, note stitching in front of first loop. 3. Hurlburt 100 loop detail. 4. Mystery (to me) belt, with woven loops, stripes, and Hurlburt type fittings?? 5. Spaulding belt.

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