Dave, I will throw some muddy water on this discussion. I was in Silverton Nov 1976 and took the attached two photos which you have identified as 04163. As far as I can make out this car is 04266
My reasoning is the end number in 1976 is 04466, but the side number is 04266.
A unique identifier for this car is the lamp vent under the roof walk.
All that said, when the same car was sold, it was identified as 04466
by the D&S.
What is even more ironic is the other 04466 was next to it in 1976.