3429th was simply the unit he was assigned to at the time of his release. 3429th probably didn't serve overseas. He obviously spent some time with Company C, 423d Infantry in the European Theater. Fourth Army and Western Antiaircraft Command spent the entire war in the U. S., meaning he saw only training and/or duty with these prior to going overseas. It's anybody's guess as to where or when (or even if) he saw duty with the 75th Division. The pin you refer to is a distinctive insigne; a regimental or battalion crest. I'll try to identify it for you as time permits. 423d Infantry was effectively destroyed 19 December 1944 at or near Schonberg, Belgium. The regiment was replenished but didn't rejoin the division until just after the war ended. The only way to accurately reconstruct his role in the war is to access records.