[Arran]

 I found some information regarding the 46-1201 Code 126 version in a copy of a Philco Service folder. It states that the Code 126 is the same as the Code 125, so I will start with what it has to say about the Code 125:

Code 125

1. This code is the same as Code 121 (shown in manual), except that it has a metal base cabinet, Part No. 10664A for the oval speaker or 10664B for the round speaker. Round and oval speakers are used interchangeably in production.
2.  In the new metal base cabinet, bullet catches in the upper section engage the metal base. To open the cabinet: Open the record door and used the thumbs to depress the bullet catches, located at the outside edges of the opening. while lifting upward on the cabinet. Fold the cabinet back. Hinged fasteners permit separating the top and the base of the cabinet.
3.  Code 125 bears the same run numbers as Code 121, because both codes use the same chassis. Code 125 started with Run 4.


Code 126


RUN 1
This code is the same as Code 125 except for the following:
a.  The 50Y6GT rectifier tube was changed to a 50X6.
b.  The octal socket for the rectifier tube was changed to a Loctal socket, Part No. 27-6138*.
RUN 2
a.   C201, .01 mf.,  400v, Part No. 30-4572, was changed to 600v, Part No. 61-0120*.
b.   C203, .01 mf.,  400v, Part No. 30-4572, was changed to 600v, Part No. 61-0120*.
RUN 3
The  i-f transformers were replaced with permeability-tuned transformers, to correct frequency drift which was caused by leakage of wax on the trimmers. This change involves the following:
a.   The first i-f transformer, Part No. 32-3968, was changed to Part No. 32-4160-1.
b.   The second i-f transformer, Part No. 32-3674*, was changed to Part No. 32-4161-1.
c.   The necessary wiring changes were made.
d.   In replacing the transformers, R301 (47,000 ohms), C301C, and C301D, all of which were inside Z301, were eliminated; to provide the necessary i-f filter, a 47,000-ohm resistor and two 100-mmf. condensers were installed, outside the i-f can.


  I would guess that since your set has a pair of permeability tuned i-f cans then it must be a Code 126 RUN 3 version.
Regards
Arran