Duplex Adjustable?

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A fellow over on TSD has us stumped as to what this is - and any more information about it so I thought since it's "British Made" maybe you lot knew something about this razor. I admit I'm stumped - I never knew Duplex made an adjustable - I'm not even sure this is "Durham Duplex". It could be something different. I also don't see the "adjustable" in the razor below.

Any ideas?