That's an interesting brand. I've never heard of them. Post a photo if you can. One quick resource to date the mitt is google the players name and look in a baseball reference at the height of a players career till the end. That will give you a rough idea. The mid 1930's into the 40's is about right. Also, buy a copy of the "Vintage Baseball Glove Catalog Source Book" for more details. Look at http://www.baseballglovecollector.com
and type in Hemsley in the search window and see what photos comes up.