Let me ask around and see what I can find out, but I believe that a "3rd Lt." was also listed as "junior 2nd Lt" and therefore the same rank insignia would apply. Ranking insignias were not as cmplex as today and therfore senoirity hadalot to do with rank. Again this might not be the definitive answer and I am going to ask around, but that seems to be my experience from my own research.