That is interesting, Suzanne. It certainly appears in the photo to be "207 INF". I double-checked, and I can find no 207th Infantry (Regiment) in my WWII reference.
There is a listing for a 207th Infantry Battalion, unit type listed as "Separate", which means that it was not an "organic" (permanent) part of a larger organization (such as an infantry division). Perhaps the citation on his stone referred to this unit? Perhaps this was a deviation from the convention of using "infantry" to refer to an infantry regiment because of limited space on the stone? I can only guess at an answer to this apparent puzzle. The reference shows their service from Sept 1943 to Feb 1946, all in the Dutch West Indies and Trinidad, no European service.
I think the gentleman's suggestion that you send for his Individual Deceased Personnel File (IDPF) may represent your best chance of finding answers.