All the calibration means for Stouffer step wedges, is that they've read the steps with a densitometer that's traceable to the national standard. The readings are written down on the envelope that holds the wedge.

Stouffer's makes an economical five step wedge (including film base plus fog) that will work fine. This wedge also includes readings near 1, 2, 3, and 4. (The fb+f reading will be about 0.05.)

After zeroing, I adjust the slope setting so that the densitometer correctly reads the "3" wedge, and I also check to make sure that the readings of the "1", "2", and "4" steps are appropriate. After this, I may check the zero again, and if I change it at all, I would recheck the slope setting.