Providing it hasn't been altered in any way, the clues for dating your Grandfather's box are:
LOGO- that style was phased out after the war, and was replaced completely by 1948 with the rectangular label.
HANDLES- that version was present throughout the 40's and 50's, but the rivets that hold it on went from a coppery luster to a zinc luster during the war, and then back again, can't tell from your pictures.
TRIM- The vertical chrome trim pieces narrow it down a lot. Only present on the first ones produced before the war, and then again after the war, so that rules out 41-45, though I've been told the chrome wasn't removed before '42.
If you could provide another picture or two, the way the sub assembly for the friction slides, at the very top edge, this was a folded over edge after '46 or so, but was a straight edge in the original configuration. I've also seen different weld points attaching the sides and back to the base, but I don't have a clear idea when those changes occurred.
My guess is it's the earliest production, 38~41. That's a real beauty, keep it dry, it'll last forever.
EDIT Does it have the tambour door still? Look behind the hinged lock plate.
EDIT picture of the door
![20141119_124607999.jpg](./download/file.php?id=947&sid=7d7cf6e877119c550c6acd83d8ee5a6f)
- 20141119_124607999.jpg (223.47 KiB) Viewed 1343 times