There seems to be something strange with that transaction. I don't know there, but where I live, that kind of transaction would clearly be invalidated if taken

There seems to be something strange with that transaction. I don't know there, but where I live, that kind of transaction would clearly be invalidated if taken to court. At least here, for a transaction to be valid, both parties must be in the same kind of conditions, regarding to the knowledge of the thing (if one does not know what the object is, they should explain the other, not just take advantage of the situation). This was clearly not the case. "It may also be sued annulment or amendment of legal acts when one party exploiting the need, lightness or inexperience of the other, obtained through them an obviously disproportionate and unjustified financial advantage." Spending just a few seconds in google, it seems that it is the same in other countries: "When anyone, exploiting the sum ignorance, notorious inexperience or extreme misery of another, obtains an excessive profit that is clearly disproportionate to what he in turn agrees, the injured party is entitled to seek rescission of the contract, and if it impossible equitable reduction obligation." But of course, it all depends of the law of the place. If that that's OK in Essex, well... too bad for the one selling this object. And good for the museum taking advantage of that opportunity (even if it may sound a little bit unfair). At least this machine will be in good hands. In any case, it'd be nice if they stop bragging about that. ----- Edit: And according to wikipedia[1]: In English Law, "unilateral mistake is where only one party to a contract is mistaken as to the terms or subject-matter. The courts will uphold such a contract unless it was determined that the non-mistaken party was aware of the mistake and tried to take advantage of the mistake" IANAL, but in this case, I think there was obviously one party that didn't know what the object was, and another that did know and was taking advantage of the situation ("It was advertised as a telegram machine ", "keep the change" and all that). [1] https://en.wikipedia.org/wiki/Mistakes_in_English_law https://en.wikipedia.org/wiki/Mistakes_in_English_law