I spotted an Ebay ad for 6 tin cases, 1"X2.5" X 4", and thought that might be what I could use to enclose a couple of pre-amps for my digital readouts so I took a chance and ordered them. (Hoping for good shielding.) I was successful making two of them and kept the other four for later projects.
Getting into a slew of Zeners and learning about them, (mainly from this forum), I was told about measuring them for accuracy and the idea came to me to try to make such a unit. Voila!! I did and it works!! I found that the best tool for holes in tin is the nibbler!

Jeeze! You gotta love this group! LOL It's keeping me out of the beer joints, pool halls and saloons with all of those dancing gals and wicked city women. LOL (Oh yah!! I watch those true to life western movies!!)
And for my next project ... ? We'll see.
Charlie!