This is the US DD which dates it 1907-1911 (the company relocated manufacture to Sheffield in 1911) so would that make Durham Duplexiu historically the first disposable straight?
I'm not anywhere near an authority, but as far as disposable blade straights go, I think the DD is probably the first. There are definitely replaceable blade frame backs that date to earlier, so the concept wasn't original to Durham as far as changing out a blade in a straight style razor.