Private Lugnutz said:
"Based on the SUPER and the Forged Select Steel branding, I looked through a few catalogs ranging from late 40's to 60's, but there are no matches. In fact, there are no DBE sets offered in roll-ups at all. There are DOE and combo wrench sets in roll-ups, but the DBE's were only shown coming separately or in Klip-Tites..."
Correct.
Private Lugnutz said:
"... and were given part number 910-7K"
Exactly. It is worth noting at this point that the
K suffix was also used on "kits" which came in vinyl pouches. You could buy the tiny model 350 8-piece "Vest Pocket" 1/4" hex drive set as a 350K, which came in a vinyl pouch (as opposed to the stamped steel holder.) This was true on many of the hex-drive "Handy" sets as well as some other items (such as my model 135
TK set of tiny screwdrivers - the "T" obviously indicating "treasure" - posted up-thread and in the screwdriver thread.)
Although this is not relevant to
this discussion, I point it out only to note that the "
K" suffix was not limited only to "Klip-Tite" sets in stamped steel holders.
It is also worth noting at this point that not all "Klip-Tite" sets used part numbers ending in "
K". (see 1948 Indestro Catalog No. 16, page 48 - bottom - 930-5P, 930-6P, 940-5P, 940-6P)
Private Lugnutz said:
"... 7R, which I assume is for Rollup."
I ran a search on both the 1937 and the 1948 Indestro Distributor Net Price lists on the letter
R

1937 (blue) and 1948 (white) Indestro Distributor Net Price Lists - Part Numbers with "R" suffix
The evidence you provide in the form of a roll-up pouch with the part number clearly stamped on it, and evidence in the form of printed price lists showing they used the suffix "R" on wrench sets in rolls makes it pretty clear that your assumption is absolutely correct, notwithstanding model 910-7R not appearing in any of the documentation that we currently have.
Private Lugnutz said:
"... all the color schemes I saw were red, except for some blue boxes in the 1948 cat[alog]..."
"When was Indestro's "Blue Period", 4.C?!

"
The 1937 catalog unfortunately is all in black and white. The 1948 catalog shows sets in light cobalt blue boxes, like the little 1/4" drive "D-I" set that I shipped out recently. (see below)
But it's rather doubtful that "D-I" set (pictured below) was manufactured in 1948 - it was most likely made much earlier.
In the late 1950s they were shipping out "Select" sets in blue boxes, but it was a metallic blue, and much lighter than those mentioned above - more like 1967 Ford Fairlane
Acapulco Blue. (see below)
From my observations here, perusing ebay listings, and innumerable back-and-forths with Don, here's my best guess:
They phased out the dark forest-green boxes with the fancy-schmantzy red-black-gold graphics at some point in the early-to-mid-1930s, then went to the "wrinkle-finish" light cobalt-blue boxes, and carried through with those until some point in the late-1940s-to-early-1950s, when they went to red boxes, as seen in the 1952 catalog No. 20.
They continued selling sets in red boxes all the way to the end in 1990.
"Select" sets appeared in the early 1960s in the lighter metallic blue boxes. Indestro's Trademark (733592) claims first use of Mar 21 1961.
When we brought the line into the warehouse in 1970, some of the MPI sets were coming in metallic "hammertone" copper colored boxes, like my original 3/8" drive set. (see below).
Private Lugnutz said:
"... I am reading 910-7R as 7 wrenches in a Roll-up. But can't seem to find a cat ref."
Occam's Razor says you are correct, and that part number does not show up in any of the documentation we currently have.
Private Lugnutz said:
"Have you ever seen any 910-7R before? And have you ever seen any blue roll-up, for any wrenches, (DOE, etc) before?"
No, and never.