I found several articles in Popular Science magazine that describe
aluminum rectifiers:
November, 1920:
http://bit.ly/mSK9D9
September, 1933
http://bit.ly/mnJ7JX
April, 1925
http://bit.ly/kuJa79
June, 1923
http://bit.ly/mRvmjc
I like to read old magazine copy (particularly the advertisements)
because it reinforces the idea that there's really nothing new under
the sun.
In 1920, there were wireless telephones, optical scanners (for
text)...
--Chuck