Submission of a "working model" of an invention which a patent was applied for was a requirement of US law & patent office regulation in the 1870's. http://en.wikipedia.org/wiki/Patent_model Clemens' first two patents would have fallen under this requirement. (The 1883 Memory Builder / history game would not have). Does that mean that hand-crafted "working models" of his adjustable elastic strap and scrap-book might still be banging around somewhere? DDD