T-Shirt Rabbit Hole

I have a couple of Leica T-Shirts. Above is a picture of one of them. I got it because I liked it, as one does with shirts like this.Then today I got to thinking about what is the lens that is represented on the shirt. What indeed...From looking at the lens you can immediately tell that it's likely an old lens since there are only four elements in three groups. (Layman's translation: the pair of lens elements on the right side are made of different types of glass and are cemented together. Since they are attached they count as a group. The other two elements are by themselves so they each are considered a group by themselves)Newer lens designs generally call for many more elements to correct for various image issues that might arise. (Yes, exceptions happen... the Leica 90mm f/4 only has four elements in four groups... it's also way easier with a longer lens)So then I started to Google lens formulas and quickly found the Tessar.This turns out to be (as you can tell by the year) an old design for a lens.Next up is looking to see what is the actual Leica lens that has this design...Finally, after an hour of digging around online I found an article with a low-res version of a 5cm f/3.5 lens. (Yes, so old that it was a 5cm not a 50mm lens)More digging found this:Which matches the t-shirt precisely!Mystery: Solved!This is one of the first lenses that Leica made back in the 1930s. Which is why, I suppose, they put it on a shirt.The cool thing is if I can find one of these (they might have one sitting at my local camera store, likely a slightly updated f/2.8 version) I can still mount it on my Leica M and have it work exactly how it was supposed to. Even though it'll be perhaps 70 years old.