These cooling fins may be the best engineered fins ever made for an audio amplifier.   They are the result of a strong interest in thermodynamics I had at the time. The fins are much thicker at the base than ordinary fins - and is gradually made thinner outwards.  This was done to improve heat transfer throught the fins and at the same time ensure a well defined air flow, and to get an even surface temperature, thus the lowest overall heat transfer resistance.

The fins were very carefully designed, and every aspect was calculated to give optimal performance.  The compromise - size and weight - was found to be acceptable to the gained performance.

If you take a closer look at a fin:

Note the zig-zag pattern. This was done to increase the overall surface area of the fin with 40%, not bad, huh ?

We made a few tens of these fins, and they performed as intended.  However, none ever made it into a commercial amplifier.