Inside the lid of the carrying case of the typewriter, there is a nicely cut-out image of the typewriter itself.
This label is present in more (all?) of the early Underwood 4-bank portable cases, so almost certainly this was pasted inside the lid by Underwood themselves.
It's a nice touch. Having looked at it a bit more, did start to wonder what the reason was behind this little pasted label. As owner, you'd know this was the lid for your Underwood 4-bank. In the 1920s it would I think anyhow be most unusual for anyone to own more than one portable typewriter. And a shop or dealer would for sure know to match a lid with the correct typewriter.
There is no additional text or advertising copy - and that would in any case be a bit late; when looking at the inside of the lid, the viewer most likely already is the owner of the machine. For adding advertising copy to the machine, a more likely chosen solution would have been to visibly stow e.g. the instruction leaflet (as e.g. on some Royal portable).
Perhaps it was simply an expression of the pride they took in their new 4-bank Standard Portable. (Do late 3-bank Portables have a 3-bank picture inside the lid?)
The decision for the extra cost of making and pasting this label was probably documented and written about in Underwood company internal memo's and work instructions. These will however all be long gone.
So whilst it's a nice touch, it does leave me wondering on the thinking behind it.