Clocks using the Telechron type F motor were introduced in 1932. The field coil unit is similar to that for the type B. The rotor unit is smaller than a type B rotor because one reduction gear was eliminated, increasing the output speed from 1 revolution per minute to 3.6 revolutions per minute. Type F rotors have a two piece housing, with the main body being a die cast piece. Type F rotors for alarm clocks have a long shaft on the output pinion, and those for time only clocks have a short shaft (thanks to Jay Kennan for clarifying this).
Clocks using the type H motor were introduced in 1937. The type H also has an output speed of 3.6 revolutions per minute. As far as I can tell, the difference between the type F and type H rotor is the housing. Some early H rotors have a long shaft output pinion, but most have the short shaft. The H motor became standard for domestic clocks, and was used for many years.
The meaning of the designations after the motor type (such as the H3 HNK or H3-HP) are unknown to me. Likewise with the "M" number and the number under that. They may be date or batch codes.
The most recently made H rotors (from the 1970's and on) have aluminum housings.
I have two other early H rotors with mounting feet. They are labeled:
H-3 TOP M1313
3.6 RPM 60-C 99_
60-3 6 710
There is no company name on either rotor
I have two type F rotors with standard length output pinion. They are both labeled as follows:
60-3 6 512
The letter in a clock's model number indicates the type of motor it was originally designed for. For example, a 7H98 uses an H motor. Some clocks with F in the model number contain an H motor. A 7F59 contained the F1 rotor shown at the top of this page. Models 2F02, F 327*, 7F71 and 8F03 that I examined had a standard silver color H rotor. An alarm clock made for a type F motor would have been designed for the long shaft pinion. But starting in 1937 the same model would have been made to take the short shaft type H motor.
*Note on the F 327. This clock is listed as model 327 in Jim Linz's Telechron clock book. Here is a theory: Since model 327 was introduced in 1931, but the F motor was not introduced until 1932, the first ones had "B" motors. When the clock was redesigned to use the "F" motor, the F was added before the model number to identify this change.
Time only clocks made for a type F motor can have a regular type H motor put in. But alarm clocks made for a type F rotor were made for the long shaft output pinion, and needed the special long shaft H rotor when the original F rotor went bad.
Thanks to Jay Kennan for clarifying the dates of the F and H motors, and for explaining that the long shaft F rotors were for alarm clocks. Visit his Pappy's Telechron Clock Page for more history, and beautiful photos of hundreds of Telechron clocks.
Wanted: Old F and H rotors - working or not! Paying up to $1.00 each for H rotors such as the nickel plated or copper ones shown below (or brass ones). The housing must be undamaged and have no holes drilled in it. I'll accept the the newer aluminum rotors as a donation, but will not pay for them. if you can help.