I looked at some of my items, and, unfortunately, still could not confirm the existence of any De La Rue (with smaller perforation holes and top right and left perf teeth wider). Luckily, I own the 1 pound green, which was only printed by Waterlow. This is Scott 176 and is identified as Perforation holes larger and evenly spaced. What I did was use the USB microscope to compare the top perfs of the 176 with various other items.
In all of these, the known Waterlow (Scott 176) is shown on the bottom.
I first compared it to what I thought was Scott 173, the 2sh6p dark brown. I think the size and shape of the perf holes align well, so I am going to continue call this one a 173.

I flipped the same 173 to see if there was any issues with the top right and top left perf teeth. I don't see anything.


I then found one that I thought was 173a, the De La Rue. If correct, then I would expect to see something with those perf teeth. I don't think so, but I could be wrong.

Finally, for a full comparison, I checked this against 181, the Bradbury 10sh blue. This should have larger holes and evenly spaced. The hole sizes seem to match very well.

So, bottom line is that I still don't think I have a De La Rue stamp. Does anyone have a good example to post for us?