Plunger A10 Speedo

[Jackson]

I'm putting my 53 A10 back together now.
The Speedo doesn't look right, it's not chronometric  and has serial no SC S309/00 1584, it only runs up to 80mph.
I'm told that the correct speedo is an S608.
Does anyone know what the S309 is off and where I can get a proper speedo ?
Any help greatly appreciated.
Regards,
Adrian.

[Jackson]

I completely misread the speedo serial number.
Look like it may be chronometric.
The one I have on the A10 is an SC 5309/00 1584.
Does anyone know what this speedo belongs to.?
Regards,
Adrian

[Jackson]

Finally found it.
It belongs to an Ariel Leader!
Now I need to find the right article for the A10 🙂
Adrian