If you are looking for AC Fans from Mechatronics, you may find some part numbers have the suffix “6” without a meaning for the suffix listed on the datasheet.
Confirmed by manufacturer, the 6 calls out PWM speed control, such as LPH12A99-BWHR-B1+6. B1+6 means that it has both the tachometer (indicated by the 1) and PWM (indicated by the 6).
Applicable part numbers
LPH12A99-BTHR-B1+6-ND
1570-1938-ND
LPH12A99-BTHR-B1+6
LPH12A99-BWHR-B1+6