The unknown soldier shown is wearing officer's lapel insignias and above his right pocket, the Distinguished Unit Ribbon. That ribbon narrows his unit down to one of only 18 TD units. The Distinguished Unit award would later be renamed as the Presidential Unit Citation.
A nice shot of a couple provided by site contributor, Larry Stevens. The soldier has no ribbons so this may have been taken during his training in the U.S. and probably prior to shipping to Europe or the Pacific. This may even be their wedding photo. Thanks again Larry!