Why does a certificate of calibration come with the FG-101 and FG-101B and not the FG-100 or FG-100B?

The HAKKO FG-100, FG-100B, FG-101, and FG-101B can be calibrated.  The HAKKO FG-101 and FG-101B are sold by default with a certificate of calibration due to market demand.

While the HAKKO FG-100 and FG-100B do not come with a certificate of calibration by default, one can be purchased with either unit at the time of order.