Chivas Regal 12 Year Old

This may be strange to you but, I was given an open Chivas Regal 12 year old by a close friend of mine. I have similar full genuine bottles which i bring with me from the uk and i compared the case and bottle to the ones i bought from the uk. I would like to know if there is a43% vol on the Chivas Regal aged 12 years as all the ones i have are 40 %? who could advise me on how to check if this is an original? The taste is slighlty different on the 43 % which could be a result of the 43% volume assuming it is an original?

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