Only a few in the world I know of.
This is very rare because it has the Mottled brown, Old Gold and Silver Oxide. I have never seen a Silver oxide telephone and so this is the only way to know what one would have looked like.
This is the ultimate GPO collector’s piece to place in the cabinet with your 162 in all the colours. I would think only a few in the world. I have a number of his telephones to sell for him and so if you want to contact him direct I will provide his telephone number once you have left me your full details.