Sorry Ken, not sure what you are asking. Are you wondering what the source of the specification was? I don't know where he obtained the copies of the specifications. I should clarify that the specifications I am making reference to were provided to the manufacturers and specify how the smocks were to be made (assembled) and includes specifics of measurements for each size of smock (which is great for comparing how accurate (or not) some of the modern reproduction smocks are).
I should have mentioned in my previous quote about the packing of the smocks that it was from Specification No. U/1486A which was issued 14-6-4? (last number was cut off during photocopying).