I can't tell you what I know, but I knew it before anybody else!

Seriously, I am somewhat familiar with the altenbergers. I remember their dual-pivot design(nothing new under the sun is there-anatomic cut out saddles pre-date ww1).

They were an economy type brake with relatively cheap stampings and were found on entry level bike boom bikes. Very soft through the lever.

Shimano has beefed up the design quite significantly with modern manufacturing techniques available. Campagnolo has followed suit.

I still don't think I need that much more braking than a single pivot though and still prefer their lighter weight.