The Astra 680 was introduced in 1981. It's a variation of the model 250 with minor changes in the shape of the frame and recoil shield. This might just have been to make manufacture easier. Both my 680 INOX and the 680 AL I have for sale have 6-shot cylinders, this is a definite improvement over the traditional 5-shot snubbies.
The 680 was available in blue, stainless (INOX) and with an alloy (aliminium?) frame (680 AL, which weights 450 grams unloaded).