one could drill the small holes there.
In my experience, I'd break too many 1 mm drill bits doing this.
It is not a problem if you have a mini drill press (I have such machine, acquired for less than $100 on Amazon) and the the drilling bits made from the hardened steel. One - two bits would be enough to make one hundred holes. Sure, it would take some time to make 100 holes but the advantages of them over depressions on the plate surface are obvious for all potential cases when such encrypted plate could be used.