My father served the US Army in Vietnam. I've come accross a photo from 1969 where he has on a tannish class B uniform with the 25th Inf patch on his left chest pocket, but he also has a blue or possibly purple patch on his left arm. This patch my have some yellow or white in the middle of it. May have both, not sure. The blue or purple takes up the outside edge of the patch and is shaped similar to a diamond with rounded or squared corners, but the lowest point is elongated and is the only one that appears to come to a point. I can tell you he was a mortarman and he was in vietnam. Thank you for your help.