Interestingly, I ran across several nickel plated 9mm that were berdan primed from range pickup. I also have a tendency to peer into my shell casings before running them through (most of the time at any rate)...
my system is when unloading the picked up brass from the range, I sit it on top of the bench/or table so as to sort, its easier to look at the size with it sitting on a flat surface than to look at every head stamp to see the size/caliber.
when you shoot a few calibers its easy to look at a case and assume its a certain size and its not.
thats how I get 40 S & W cases as they are about the same length as 38 Super and the same diameter as 10 MM.
anyway while the cases are sitting on the table/bench I simply look down into them as I am placing them in the dirty brass coffee cans for later cleaning and sizing.
2 holes are easily spotted.