Postal Rates and Overland Mail Surcharges

Eastwards bounded rates from USA

Postage Rate USA - Iraq (Standard UPU Foreign Rate, surface mail)
(Date Format dd.mm.yyyy)

Surcharge for the use of Overland Mail
Reference: the "United States Official Postal Guide"

The July 1927 guide also states that mail intended for this service should have a label with the words "By Overland mail, Baghdad-Haifa" or be prominently marked. 

The July 1933 Guide indicates that mail for this service is to be marked "By Overland mail, Jerusalem-Bagdad

So far I am only aware of 2 postal cachets from the Post Office New York, based on a letter dated November 7, 1926 as shown below (collection Zvi Alexander)

The text of the 2 cachets reads as follows:
On front of the cover:
Dispatched By Ordinary Route / Fee Not Fully Paid / Baghdad – Haifa Motor Route / P.O. New York, USA

On Back of the cover:
This letter insufficiently prepaid for the route indicated on the envelope / Haifa – Baghdad Motor Route / Cairo – Baghdad Air… / … be prepaid 6 cents per ounce in addition to the regular foreign postage. (Post Office, New York, USA).