I saw on another website that collector said that the only difference between the Yorktowne and the Clark models was that the Yorktowne came in a 10k gold filled case and the Clark came in a 14k gold filled case.
What say you Hamilton experts?

Tony,
In Rene Rondeau's book, the Clark and Yorktowne are both gold filled. The cases are quite different too. The Clark appears to be in a fancy rectangular case and the latter is a long tonneau shaped case.

The cases of the Yorktowne and the Clark are indeed the same except for the case material... at least the FIRST version of the Clark. There was a SECOND version of the Clark that appeared in 1955 with a small square case and very long triangular-shaped "bat ear" lugs, which is obviously different from the Yorktowne.

The first version of the Clark appeared on September 1, 1936 with either an applied gold numeral dial (dial #D-27) or enamel inlaid numeral and marker dial (dial #D-28). This watch had a 14/0 size grade 980 movement and 14K yellow gold filled case.

On January 25, 1940, Hamilton announced that the grade 980 movement would now be used only in 10K gold filled watches, instead of 14K gold filled watches as previously. Up until 1940, Hamilton had not offered the 14/0 size movement in 10K gold filled. This is when the Yorktowne appeared... February 13, 1940... and is the result of Hamilton introducing the grade 982M movement and re-organizing how the remaining grade 982 and 980 movements were assigned into the various types of case materials.

Up until 1940, the grade 980 was cased in 14K gold filled only, and the 982 was cased in platinum and solid gold only.

Beginning in 1940, the grade 980 was cased in 10K gold filled only (not previously used in 14/0 size watches), the grade 982 was now cased in 14K gold filled only, and the new grade 982M was cased in platinum and solid gold only.

Hamilton's records show that when the Yorktowne appeared on February 13, 1940, it was dialed with dial #D-27... the very same applied gold numeral dial previously used on the 1936 version of the Clark.

So, if you look at the first version of the Clark and the Yorktowne, they are identical except for the case material... and are identical in Hamilton's catalogs and thus are identical in Rene Rondeau's book since he used the catalog illustrations to illustrate his book.

Bryan,
Thank you for the update on the Clark-1936 and the Yorktowne-1940. Are there any other Hamilton ww that are almost identical?

Yes, there are a few more Hamilton models that have identical case shapes, but different names due to differing case metals or dials. Here are a few:

The Aldrich and the Sherwood M have identical 14K gold cases, but the Sherwood M has a wood dial.

The Brock and the Cambridge have the same case, except that the Brock is 14K and the Cambridge is platinum.

The Donald and the Turner have the same case, except the Donald is 14K and the Turner is 10K.

The Morley and the Douglas have the same 10K yellow gold filled case, but the Douglas has a coral finish dial with rhodium plated numbers that look like white gold.

I'm sure I can come up with some others.

Tony,
I do apologise. I looked at the wrong year Clark.

In Hamilton's Series I cld models the Langdon is 10k gf and the Lange is 14k, Nordon is 10k gf and the Norde is 14k. The pictures are on page 123 of the Swigart "Illustrated Manual of American Watches"

Jim,
Also the Clinton 1936 version avalable in white and yellow goldfill and the Greely sterling silver.