I used to do a lot of work on Royal Yeomanry armoured vehicles, from Saladin, Saracen, Ferret, Fox and CVR(T) when they were brought into our workshops.. The HQ squadron was at Westminster (Westminster Dragoons). C Squadron was based at Croydon., they were Kent & County of London Yeomanry. The other squadrons were based around the country so yes it would require on the record card. I am sure the R Yeo LAD was at Croydon as I recall going up there to sort a problem out on their Leyland heavy recovery. What army registration number is your Ferret?