This mitt has been discussed on and off the glove forum as well. I don't think it has any support as a baseball mitt. If it were a basemitt, it very likely would have been known through catalog images before surfacing, and that hasn't happened. Additionally, though the back is very well made, the front isn't of the same standard. Its shape suggests something other than catching - even the earliest gloves and mitts had a shape that was purpose-made to protect during the act of catching a ball in flight. This doesn't look like it would collapse in any way that would ever form a pocket for the ball.
http://www.vintagebaseballgloveforum...hp?f=10&t=5060