The ears have it......I believe they are mules now looking at it. I also believe it is the same sculpted mule, but dressed differently for the two photo ops to display how the gun and carriage was carried. Maybe a promo of sorts.

I agree that these (this) mannequin is not the same type as that shown at Rock Island Arsenal. The one at the arsenal is likely made of wire and plaster covered with a real horse hide. The sculpture in your picture is likely made of one homogenous material as the tail does not appear to be real hair. The base may be of the same type as show at R.I.A.