Posted 10 February 2016 - 09:12
As a former student of German L&L I may be able to shed some light on this. It is indeed true that the penultimate reform of the German orthography around the beginning of the 20th century rendered the German "th" obsolete, to be replaced by a simple "t". Of course, this applied not necessarily to names, and old habits die hard, which would explain why his name could actually have been Helmuth instead of the more modern form Helmut. From there, it may have been a personal preference to use the "h" or not, signifying either tradition or modernism.
I can understand the importance of getting the spelling right, particularly since I'm in the lengthy (and tedious) process of "cleaning" my data bases to make them unambiguous for a computer program - e.g. Jim Clark should always be refered to under this one name, not Jimmy or Jimmie Clark, yet the programme needs to be able to understand that the (hypothetical) Jim Clark who races Midgets in Southern Iowa is not the same person - but there is no difference between the names Helmut and Helmuth from a linguistic (or social) perspective. Names do change over time, the same as language. Heck, I have a relative doing genealogy in the 17th and 18th century, and the changes in spelling are simply mind-boggling; this here is just kid's stuff.
Long post short, there will be no simple answer. Maybe his birth certificate shows a different spelling from his death certificate, which one are you going to chose? Personal preference prevails.
