I consulted with my colleagues at Defense Security Cooperation University (DSCU).  This is what they provided me on this topic:

The SAMM C7.6.3 (DTS Documentation Requirements) states: "The following paragraphs outline general and mode-specific documentation requirements.  C7.6.3.1. If a shipment is released from a depot, an Issue Release Receipt Document (DD Form 1348-1A) identifies materiel as DoD-supplied and provides the details (document number, case designator, National Stock Number, etc.) that link the materiel to a case. If a shipment is released from a vendor under a DoD contract, a IRAPT Receiving Report (formerly Wide Area Work Flow Receiving Report and DD-250) serves the same purposes and provides the same data. MIL-STD-129 requires that shippers attach at least one copy of these documents to the exterior of the shipment units in waterproof envelopes. One copy must be inside the container. Commercial invoices and certificates of origin may be required for in-country customs clearance."

The SAMM and Greenbook also mention that the DD Form 645 ( DD645 is the FMS Bill) and Commercial Bill of Lading can be used as proof of title transfer. Please see more detail below.

The Standard Terms and Conditions (within the LOA) Section 5.4 asserts "The Purchaser agrees to accept DD Forms 645 or other delivery documents as evidence that title has passed and the items have been delivered."

Greenbook 8-13/8-14 Section 5.1 Title Transfer and Delivery Point Section

5.1 identifies where the title transfers and delivery occur. Title represents ownership. Delivery, in this context, does not mean the material has arrived at the final international partner's destination. Delivery refers to the point where transportation responsibility transfers from the USG to the international partner.