I really doubt that SIPCO made your Case. Therefore, I researched it deeper.
I am quite certain that your Case was manufactured by The Green-Case Co., Racine WI around the late 1920’s.
They are not in ‘The’ Guide because they only offered plywood cases that were metal covered, no all hardwood. The Union Green-Iron are also not included.
Green-Case’s 0/5 Case has the same dimensions as your 0/5 (the 10 ¾ dimension of yours would be 10 ½ if no hardware was included). The drawer guides are near the bottom of the drawers, the drawer beads are on top and the front cover luggage lock are all the same. It is rare, Good luck…..Ted
D@mmit, I've been down this road before, and I missed an important clue along the way!

Those names quoted above sounded familiar.
Starting here,
@four.cycle asked a question, and I dug into the answer
What's the story on that? I am well versed in the history of Simonsen and the heavier duty versions of these cantilevered hip roof tyle boxes they made for the US Army Air Forces (Mechanics, Type II, Class A, Size 2), before and during WWII through the early 50's when they got rounded corners...
www.garagejournal.com
I apparently did not look at the pdf in this post, as my box is there.



What's the story on that? I am well versed in the history of Simonsen and the heavier duty versions of these cantilevered hip roof tyle boxes they made for the US Army Air Forces (Mechanics, Type II, Class A, Size 2), before and during WWII through the early 50's when they got rounded corners...
www.garagejournal.com
So, looking at how both the Green-Case and the SIPCO have the top bead, and they were both in Racine, wonder if the "case making" part of the Baker Case business was sold. SIPCO was not known for tool chests prior to what 1938.
Looking into the google search of
"baker case" sipco
gives this as the first answer, in the FB group
Antique & Vintage Wooden Tool Chests & Cases
Was hoping to find some contemporaneous proof of this, so I dug further, but no luck
There are also references to a certain "guide" included in those search results
Going into Books, there is a Hardware Age V144 Issue 1-4 pg 444 from 1939, but no preview. But fortunately ITCL to the rescue, but all it gives is this
Searching for "baker case" schartow gives the same answers
This does give an interesting view into what all Schartow was selling
Hardware Age 1939-07-27: Volume 144, Issue 2.Digitized from IA1574615-04.Previous issue: sim_hardware-age-home-improvement-market_1939-07-13_144_1.Next issue:...
archive.org
Boxes, Flower
Buttons, Door (see also Pulls, door)
Chests, tool as noted above
Corners, Box, Chest and table
Hinges, cabinet
Only thing missing from the tool box was the top handle
Thanks Ted for the Pointer back to Green-Case and Baker-Case. Gotta go look closer to see if I see any remnants of a decal.
Now back to edit some posts...
Continuing the digging between calls, in 1935 Racine city directory, I found this. They were in the same block

That's a train track to the right of my red line (at the top)
Here is a 1925ish map
