As far as I know, this is a 1912 Clutch Drive Plate...as to how long this style was used I'm a bit foggy on that. I know that there was a major change in 1916 with the addition of the plug in the interior of the shaft. I've seen pictures of a 1912 clutch drive plate with these clutch fingers...they're different from later years in that they have not flats on the sides like the ones in the 20's. Which if you think about it makes sense in that there would be subtle changes to these as the years progressed...I think.
Anyhoo, if any of you who have 1915 cars and have had the transmission apart and they're different than what I've drawn here and if you've got pictures of your clutch drive plate please send them to me. I'd like to get these correct as much as possible, thanks.