Question

翻译成英文：“本合同书自三方代表签字并盖章之日起生效，一式三份，三方各持一份。”

Answer 1

This contract becomes effective since the third party representative signs and seals, triplicate and each party holds one copy

Answer 2

This contract will be valid on the date when the three parties sign with respective official seal. There are three copies of the contract; each party is to hold one copy.

Answer 3

The contract becomes valid from the date of signing and stamping by all three parties. It has three counterparts, each of which is held by one party.

Answer 4

The contract will be valid since it is signed and sealed by three parties.There are three copies and each party get one.

Answer 5

The contract/agreement becomes effective from the date of signing and stamping by all three parties. It has three (3) conterparts, each of which is held by one party.
还可翻为：
The contract/agreement becomes effective from the date when all three (3) parties sign and stamp on it. It is made in three (3) originals, each party holding one.