Hi, I've gotten this Herr Standard that needs the suspension unit replaced. The TimeSavers Catalouge lists four for the Standard! #20A 54, #20B 54, #27A 53, and#27B 55. Do those relate to the Lenght? There are No markings on the back of the Movenent except to say it's German, (0) Jewels, Unadjusted. How do I determine Which Unit to Order?