First, regarding the manufacture of Mills belts, the earliest would be 1879 when, according to R. Stephen Dorsey in his book "American Military Belts and Related Equipments", Anson Mills began manufacturing woven belts on a loom purchased in Worcester, Mass.
Dorsey's book illustrates several woven belts for .45 caliber rifles and carbines in the 1880s. If you can find a copy (ISBN: 0-913150-49-5), you may be able to identify your belt.
Another option is to post photos, front and back, so it can be examined and possibly identified by me or another member of The Company.
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