Per Lord Macnaghten in James Drummond & Sons v E.H. Van Ingen & Co (1887) 12 App.Cas. 284 at p.297:
After all, the office of a sample is to present to the eye the real meaning and intention of the parties with regard to the subject-matter of the contract which, owing to the imperfection of language, it may be difficult or impossible to express in words. The sample speaks for itself. But it cannot be treated as saying more than such a sample would tell a merchant of the class to which the buyer belongs, using due care and diligence, and appealing to it in the ordinary way and with the knowledge possessed by merchants of that class at the time. No doubt the sample might be made to say a great deal more. Pulled to pieces and examined by unusual tests which curiosity or suspicion might suggest, it would doubtless reveal every secret of its construction. But that is not the way in which business is done in this country. Some confidence there must be between merchant and manufacturer, in matters exclusively within the province of the manufacturer, the merchant relies on the manufacturer’s skill.