From pattern:

MATERIALS: These socks are knitted in a new and original slip stich sic pattern which is quite easy to do. Lady Galt Kroy 3 ply (50g): 2 balls main colour B and 1 ball contrasting colour A will make all foot sizes in both lengths. Set of four 2 1/4 mm (No. 13) (U.S. 1) knitting needles (points at both ends) or whichever needles you require to produce the tension given below.

MEASUREMENTS:
Standard Length—Length of leg to bottom of heel flap 13 1/2 ins. (11-inch leg).
Shorter Length—Length of leg to bottom of heel flap 10 1/2 incs. (8-inch leg).