Marylinpa - Have you been able to find any official records that show that William had served in WW I? On his passport application he mentions that he has travelled abroad with the navy but doesn't give dates. His father attaches a note to the application (to expediate the procedure) that states that "he served as an ensign on one of the destroyers of the late war", but doesn't give any specifics. I have not been able to find any records for William being drafted. I have found both Oliver and John (his brother's) draft cards but nothing at all for him.
ETA - On his 1940 census (when he was already in California listed as married to Anna with son Roy) he states that he never did the navy or military.
???
The informant for the census information in 1940 was Anna, not William (they mark who provided the info.) It's possible she didn't know or just didn't think about her answer (or the census taker marked it wrong.) I've seen these discrepancies often when researching my own family.
Also, any one that had already joined won't have a draft card. So perhaps that's why we don't see a draft card for him. We declared war on April 6, 1917 and the first draft registration day was 2 months later. He may have joined right away and missed the draft. My great grandfather's brother has no draft card, but he was already serving when the draft started. I have a draft card for my great grandfather.... Jmo