Gazelle? Does anyone know anything about them?

The one on the picture (Marktplaats) is the 1st version, with a smooth transition from braze-on block to tube. That's a weak spot. A crack (?) will appear on the transition in many cases. Sometimes, one half of the black may fall off completely.

Just to illustrate what Dutch Cheese stated some time ago, here's a picture of my AA Special frames seat clamp:

I saw the same sort of crack on an AA frame a friend of me bought recently. I didn't notice that crack for a long time, but recently the frame started to produce some strange sounds when riding - and i already sorted out all other possible sources like bottom bracket, cranks...

Now i'm courious for how long the clamp will hold...