It was a pre-emptive measure too as rifles could be ordered with this feature from new. I don't think anyone would have necessarily gone to the expense of having selous plates made and fitted (quite time consuming and costly) when the wood on early Farquharson's was not particularly special generally and could be replaced more cheaply. It is not impossible though...
Rifles with Selous plates are relatively rare and mainly on a few Gibbs rifles, although Winfer's book shows some others, including a Holland and an Evans - IIRC