That looks to be in very good condition and $40 shipped is hard to beat, considering it's probably about the price of the shipping alone. I have the same model which I paid about 2.5 times as much for with shipping.
I don't remember the exact years, but a while back I managed to find some 1960s Craftsman catalogs and it seemed like they offered this particular toolbox from the early to mid 1960s. In the later 1960s catalogs the otherwise identical boxes are listed as having a wrinkled brown finish, like the modern Kennedy boxes, rather than the hammered gray finish. So, the gray ones are about a half century old, give or take a few years.
I can understand why a lot of people don't find much use for the machinist's chests, but they can be nice for storing small, clean hand tools. I just use mine for a basic assortment of household tools like screwdrivers, pliers, basic electrical tools, basic socket sets, etc. It works rather well for that, but sometimes I wish it were either an inch or two deeper OR smaller and more portable. As it is, it's a pain to lug around, but a little small for a stationary box. I definitely wouldn't use one in a garage for mechanic's tools, but of course that wasn't what they were built for. If you're not a machinist they can still make a good household project/hobby box.