Recently the subject of Al Lein's homebrew speaker impedance tester came up in a thread on the Antique Radio Forum.
I've seen some of Al Lein's homebrew test equipment on display in the back room at the Pavek Museum in Minneapolis. Al does incredibly nice work.
The Pavek Museum has a few web-pages about his gear with some nice photos. I took some photos in my visit to the Pavek and wanted to share them.