1cm calibration cube with lettered faces

Having printed quite a few 1cm calibration cubes I've stumbled upon the recurring problem of not knowing which side is which when measuring the results after tweaking (only on the x/y axis).

Therefore I made a cube with letters on each face.

T = top
G = ground
F = front
B = back
L = left
R = right

The letters are about 2 mm deep.