CAV ammeter shunt

I've got a CAV 60-0-60 ammeter with the label 5539/233AB on it which should have an external shunt but hasn't. Does anyone have a surplus one they would be willing to sell, or alternatively, know where I could get one please?

Saw this post, and I am trying to help a mate with a CAV 100-0-100 ammeter (came from an old Landrover). Did you ever locate a shunt, and if you did, do you know what the rating for the shunt was in millivolts?

I have an ammeter with a 75mv shunt, and 100-0-100 scale. But me mates CAV meter connected to my shunt looks to over read. i.e Where I was expecting it to read 6amps, it was reading 10...

This could be cos the shunt is rubbish, or because the shunt rating for the CAV ammeter should be different.

Sorry Im not a GT40 person, but I'm looking for some advice on an external shunt CAV ammeter, as fitted it appears to some GT40s.

The part number for the shunt for the CAV 100-0-100 meter is Z5913/30

thanks Matt