The Lost Tribe of Gad is modern Spain and all other affiliated countries.
Jacob's pronouncement over Gad:
19Gad will go out to raid, and will pursue at the heels of his enemies.
The term raider would end up as the Spanish term conquistador and is best know as the Spanish ships that raided Central and South American for what would be known as Spanish Gold.
Gad ended up with a considerable inheritance, including all of Central and South America.
The Treaty of Nijmegen forms the seal date document for Gad, and identifies Gad as Spain.
Curiously, on the exact seal date, a French fleet is sunk by Dutch ships in the Caribbean, which is generally Gad's territory.
The seal date for Gad identifies Spain as the core European country for the lost tribe of Gad. Portugal is also listed as part of this tribe because of the close association and language similarity between Spanish and Portuguese. This causes Portugal's former colonies to also be listed as part of Gad.
Italy is also listed here as a part of Gad. This is because of language similarities. In ancient times Italy was probably the prophetic location of Manasseh, and times when the Italian army were moving prophetically (70 AD, for example) are also matched by modern American army movements. (Kuwait invasion.) The Manasseh seal date does not include Italy, and there is essentially no reason to think modern Italy is still Manasseh.
Ethiopia is listed here because Italy was the European power that attempted to subdue the country. It should be noted that Ethiopia is one of the few countries to remain independent in Africa, similar to Thailand in Asia. There may be a better assignment.