The Extra Thin model 1 grades are very similar in appearance to the Illini but do not have DeLong's patented 5 tooth click. They were made during DeLong's term as Master Watchmaker for Illinois and it is likely that the design is his also. I have not seen any documentation to support this, but i would like it to be true. With only 19 jewels, the 437 XT come in a bit below the other watches in the Illinois Small Wonders but with the jeweled barrel, they do look very nice. There are three examples in the collection with serial numbers 3650513 (18K), 3761666 (18K) and 3761696 (GF). They are shown below.