Well, he does it ...

... The new battery. In my SL 78 H. However, he looked on the product image quality by far. The picture shows a label with a bunch was seen detailed information, such as the manufacturer's specification.
I thought to myself, with a Li-Ion battery, can be used alone for security reasons not be bad if the manufacturer is immortalized with their own name on the product. However, the supplied battery was just a pure white battery with the simple black font that it is a "High Capacity Battery" for a Gigaset SL870 with 3.7V. That was it, nothing else. Such batteries I have also in Amazon from other vendors found, but then decided to use this product because of the higher-quality translucent image. Too bad that the image does not match the delivered product)
Anyway - The battery runs. The price was definitely favorable.

Addendum: There are now raised two years in the country. The phone we have now been replaced, but it was with the battery well 1 1/2 years in use and there were no problems with the battery.