Manifoil Keyless Combination Lock. Initialy made by Milner/Chatwood-Milner. Chubb took over production and development when they aquired Chatwood Milner.
Attachment 7299
M00174 - MKII. Eccentric drive cam, 1 spring loaded roller. c.early 1950's.
Attachment 7300
M00232 - MKIIA. Second spring loaded roller added, but before shielding was added.