These aren't '7th Cavalry' winter hats - they're one of two patterns of winter clothing issued to soldiers on Northern posts.
The earliest is the 'Sealskin Cap and Gloves, Pattern 1876' - sealskin having been thought to be durable, but after issuing 8,158 caps and 7,437 pairs of gloves, it was found that it didn't hold up to the rigors of soldiering,
It was replaced by the 'Muskrat Cap, Pattern 1878' and 'Muskrat Gauntlet Gloves, pattern 1878'.
These were issued along with 'Woolen Mittens, Pattern 1873', as well as the 'Buffalo Overcoat' - probably the Pattern 1877, but there's no designated specification, merely the first year of purchase.
These overcoats were Company property - issued in Winter and stored in Summer.
When the North Russia Expeditionary Force went to Archangel during the aftermath of the Great War, many of these articles of clothing found their way there.
Vaya,
Scouts Out!