(1) Unless otherwise agreed a credit is established:

(a) As regards the customer as soon as a letter of credit is sent to him or the letter of credit or an authorized written advice of its issuance is sent to the beneficiary; and

(b) As regards the beneficiary when he receives a letter of credit or an authorized written advice of its issuance.

(2) Unless otherwise agreed once an irrevocable credit is established as regards the customer it can be modified or revoked only with the consent of the customer and once it is established as regards the beneficiary it can be modified or revoked only with his consent.

(3) Unless otherwise agreed after a revocable credit is established it may be modified or revoked by the issuer without notice to or consent from the customer or beneficiary.

(4) Notwithstanding any modification or revocation of a revocable credit any person authorized to honor or negotiate under the terms of the original credit is entitled to reimbursement for or honor of any draft or demand for payment duly honored or negotiated before receipt of notice of the modification or revocation and the issuer in turn is entitled to reimbursement from its customer.