The 1905 patent below of a catchers mitt by Burt Rogers for Victor Sporting Goods shows a face made of two pieces sewn together. Line h in the drawing is the sewn line joining the heel section to the palm section. The sewn lines are of unequal length with the palm section being longer so as to create a puckering along the sewn edge which forms a concavity which becomes the pocket of the mitt. This sewing technique is common in the leather industry to shape articles of clothing, handbags, etc.
The mitt below shows the sewn edge of the heel section joining the palm section. The sewn line is visible just above the crescent pad. A nice pocket is formed on this mitt. A pretty clever idea. Burt Rogers was one of the principals of Victor Sporting Goods who had years of glove making experience, having apprenticed in Gloversville, NY.