There are various opinions about signed casebacks. Some collectors don't like it as it distracts from original condition of the case, others like the added piece of history that comes with it. My example here has that piece of added history.
It is a Waltham Crescent Street 21 jewels model 1899, adjusted to 5 positions. Pure railroad material. It was made about 1907, and total production of the 1899 open face 21j Crescent Street was 11225 in lever set (this one) plus another 7500 in pendant set. The case is a Keystone J. Boss.
Now this caseback is marked FWS for Frank William Stevens. He passed away in 1954. He was a brakeman on the DL&W (Delaware, Lackawanna and Western Railroad) during the 1930'ies, 40'ies and early 50'ies. So it is safe to say this watch was grandfathered into service (grandfathered = a watch that has earlier passed railroad critaria will later be accepted when newer, stricter criteria are set). Anyway, it would easily have been able to meet all newer standards as it was a 21j 16s 5 positions watch.
The reason I know this is that I asked the previous owner after I actually purchased the watch. He told me that his grandfather used to teach him how to read time on this watch in the early 1950'ies. It is sad that he had to sell his heirloom, but I promise to take good care of it.
Here is a link to a Wiki article about the DL&W railway:
Delaware, Lackawanna and Western Railroad - Wikipedia, the free encyclopedia