harpgirl,
    If you can get a copy of The Autoharp Book by Becky Blackley there are pictures of the shifters and a description of how they were developed. This book is the definative authority on Autoharps.

I seem to prefer the A styles and have two appalachian "A"s and two old black box "A"s. I also have an old Chromaharp. One of the black boxes is chromatic, all the rest are diatonic.