The chest plate belonged to a SGT. Vikers of the USMC. It says it right on the front of the neck. It think the survivalist pieced that together and it just happened to look like ncr desert ranger armour.
I don t think there was any armour combo like that pre war. It think it was somthing made up for NCR vet rangers to look bad ass.
I dont know, the wiki says that armor and trench coat was made by the same people who made the ncr armor, and it was made for US marines in china.But, the wiki can be edited by any one, so who knows.