IDBiG: Implicitly-Dimensioned Binary Grid

A while back, I got an idea stuck in my head. If one wanted to, say, scratch a series of tick-marks into small bits of metal to serialize and identify them, how would one do this? Small is key here; easily printing decimal numbers may not be possible, and something like a binary number may be limited in length. The obvious solution, to me, is a flexible, two-dimensional binary grid. But what happens when you make a mark like this: