Well, I was going to leave it but PJ insists I answer it.
This a hand built "Auto-Boat" from 1929 constructed by a Mr. W.G. Daubenberger of Des Moines, Iowa.
I found rather little beyond what PJ earlier posted other than it was entirely hand built except for the motor which was from a Nash. He is trying to contact the family who apparently still reside in the city to see if he can find out more and I am still working the Internet to see if I can find anything, particularly in the Des Moines newspapers of the day or their City Historical Archives.
Bill