[Antipodal]

Thank you fellows, I have searched in the right volume of Riders (1939 PQR Page 43) and found  a  schematic  which is almost certainly the right one for this set.You were right ,Joe, it seems to be a Model 921 or 922 (Run No.2). The tube line up is correct but more importantly the  chassis parts location diagram shows the pushbutton station selector switch arms poking out the front. The other models you suggested do not seem to have this feature.As I dive into the  insides of this set I will use this schematic as my guide.What a wonderful resource we have in the Phorum.  Thank you all.
I have also noted that there are instructions on how to load photos onto the Phorum.As my grandaughter who used to help me do this has moved away I will have to swot this up and see if I can get a photo uploaded.(..Used to help me ! Pshaw ! She did it ! )