Yup, the last looks like a recently found image from WW2 I'm enjoying your efforts, discussion and results.
I have a digital Caliper Gauge (Lidl) which I use to measure card etc thickness - putting a card edge up against the hole gives you an idea how large the hole is
I used the feeler gauge to block light off the latest hole - hence around 0.2mm
I drilled out a body cap for the E-M5, put blackened painter's tape inside, and used a pin to poke a hole n the center , maybe a bit more than half a mm (using a ruler to judge) It seems to work, and I'll bring it with me when I leave the house to see what I can see. I guess I'll throw tape, a pin, and a large black sharpie in the bag too -- and a lens in case my home made pinholes don't do the job.