I believe that depended on the manufacturer and country convention. Most US keyboards didn't have an accent character. For example, here's one from the 1950s:
For acute or umlaut you could use a + backspace + ' or u + backspace + " (or the opposite order). For grave or circumflex, I don't think there was a solution. Write it in by hand?
http://www.typewriters101.com/uploads/1/7/6/6/17660651/s7662...
For acute or umlaut you could use a + backspace + ' or u + backspace + " (or the opposite order). For grave or circumflex, I don't think there was a solution. Write it in by hand?