>I'm specifically interested in understanding if you can take a Weatherly Index # from a tool catalog and accurately date it (or gain other information about it).
Probably not, from what I am reading, when you get a new catalog with index 400, it replaces obsolete catalog with index 400, so they stay in order at the counter.
So it won't help you date anything.....
On the other hand, googling for 'weatherly index" gets you a boatload of online parts catalogs, since that is printed on the cover of all of them....