LG
Isn't the 1940 catalog really the 1939?
Papaw's 1942 catalog looks like the 1941 on auction. His is copyright 1941 with a print date 4-1-42
Yes, I realize this has become quite confusing...
What I (and most others) had been calling 1939, I have come to believe is really 1940. The reasoning - as Tool Pants pointed out - is that although the date on the inside of the back cover is "6.39" or "June 1939", that seems to be the printing date or copyright date.
1939 or 1940:

The 1942 catalogue is conveniently marked as such. As you noted, this 1942 catalogue has a stated 1941 copyright and a second "4-1-42" date (presumably printing?) which is either January 4, 1942 or April 1, 1942. This seems to be a bit of an exception. Most (all?) of the other catalogues with stated date seem to have a print date inside from the prior year and that is why I am now calling the first catalogue pictured above a 1940.
1942:

The catalogue that just sold on eBay is very similar to the 1942, but is a different colour with no stated date. I have never seen this catalogue, so I don't know what the dates are printed inside, but the seller thinks it's a 1941 for some reason and we know it's not 1942 or 1939/40 so I think we can safely accept it is as 1941...
1941?:

The next issue I'm aware of is this 1948 (with a date of "11.47" inside)...
1948:
