Herewith we are sending you a written contract under seal in two copies.

兹寄上盖有印章的契约一式两份。

《新英汉大辞典》

A contract made by an urban council, whereof the value and amount exceed X50, must be under seal, and certain other formalities must be observed.

由市政厅签署的合同，若其中涉及的金额和数量超过50倍，则须盖章并履行其他手续。

youdao

Answer: effective, unless the contract agreed to sign and seal.

答：有效，除非约定合同生效需签字并盖章。

youdao

Now Dassault must seal the contract with India in a series of detailed negotiations over technology transfer and other conditions.

ECONOMIST: India favours France��s Dassault

Unlike its smaller rivals, China Mobile does not offer the iPhone but it hopes to seal a contract with Apple to begin selling the popular smartphone later this year to boost growth, according to local reports.

BBC: China Mobile profits rise in 2011 on data downloads