The style of the typewheel is on the wheel.  Its facing the platen.  MA, ME and PS are the common ones.

 

Dont run your machine without a good replacement hammer on the metal one. 

 

If you need a couple of vinyl hammers give me your address and I will send you a couple.  No charge.

 

They used to be rubber but now we are using vinyl.

 

https://wiki.theretrowagon.com/wiki/Teletype_Model_33

 

The link above will give you quite a lot of info if you want to utilize it.

 

Best regards,

 

Wayne

KB1FDW