1957:
Hard Aluminium Surfaces Ltd
Hard Aluminium Surfaces: Hard Anodic Coatings
Rec. Num. 1 of 2
Source: Flight December 20th 1957
1961:
Hard Aluminium Surfaces Ltd
Hard Aluminium Surfaces: Hard Anodising For The Lightning
Rec. Num. 2 of 2
Source: Aeroplane July 13th 1961