Before frame builders could weld or glue aluminum, they bolted it together.
You could build a retro frame like this today, copper plate it and call it Steampunk for the Tweed crowd. Your local shop would groan though, like they do when various old French bikes show up for repairs.
Spotted at Elliott Bay Bicycles, downtown Seattle.
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Caminargent?
I still see a fair number of cheap Indian bikes with bolt-together rear triangles while traveling in Africa. http://www.flickr.com/photos/bikejuju/4688316463/in/photostream/