I saw this in the MTFCA Encyclopedia for 1926 model cars:
"Automatic windshield wipers for open and closed cars will be available within the next week or ten days at the following prices: T-3318R Automatic windshield wiper (open cars), $5.00. T-3320R (closed cars), $5.00. Less 40%."
I have never seen one. Did this happen?
Yes, they have been discussed a few times on the forum: http://www.mtfca.com/discus/messages/179374/228620.html
Guess they were fragile and didn't last long in service - the surviving units seems to be mostly NOS.
The wiper motors were made for Ford by Trico. They turn up every so often, I have 5 of them. Mine have good pot metal but most do not and bad pot metal makes them impossible to repair. They are a neat accessory.