speedo question

[matches]

i have two speedo's and am wondering which is right/ original. one is a vdo speedo with two different threads on the back where the speedo cable screws on and the other is an AC speedo made in england. the vdo one has a slightly larger ripple disk in the middle than the AC one, any help would be great as both appear to be in great condition but having the option i'd like to use original. thanks L&K

[artyfartymarty]

I have an AC speedo on my FB. its the second one as the original died. the original was also AC.