A4 X1 Coder

End is Labeled:

A-4         X1    CODER                            100-101116
N             L              J         H          F            D  C  B   A
G             R             R         R          R           T   T   T  T
r               e              e          e           e            P   P   P  P
n              d              d          d          d

ICD-GPS-200

The X1A code is a shift register with the following equation:
1 + X⁶ + X⁸ + X¹¹ + X¹²

The X1B code is a shift register with the following equation:
1 + X¹ + X² + X⁵ + X⁸ + X⁹ + X¹⁰ + X¹¹ + X¹²

Where the exponents are the tap locations that are combined in an or gate and fed back to the input.

The X1 code is formed by the MOD 2 combination of X1A and X1B (i.e. a Gold Code).

I would expect to find a couple of 12 bit shift registers on this board with each bit's output brought out to a pin and some big OR gates and an external or gate to sum the codes.