A strip of material 10cm long, with a group of 5 pips and the number "5" indented into it 10 times, at each depth from .1mm to 1mm. To get a feel for how deep numbers etc should be.
Updated to have outdented numbers (turned sideways because things were a little cramped.)
10 w x
1 d x
3.937 w x
0.394 d x