A great design as it is, the 1903 Pattern belt had one small problem when used with the military equipment of the day = no rear mounted buckles for attaching the 37 Pattern webbing cross-straps.
To get around this, a 1 3/4" wide webbing belt sleeve was introduced, which was fitted with a pair of 1" brass buckles; the 1903 belt was passed through this, thereby allowing the '37 Pattern shoulder straps to be attached to the leather 1903 belt.
A simple solution, which got the job done!
An original 1942 dated example.