Schildkrot! Wow, a blast from the past! I used those here in the USA back in the 1960's and 1970's but have not seem them lately. We considered them to be a 'hard' ball. Maybe that was the suggestive power of the turtle printed on them. Now I much like the Nittaku and Butterfly 3 stars, the Butterfly has a nice soft feel to it. One thing I have learned, is that if a batch of balls feels too soft to you, you can put it on the shelf for a year (just be sure to rupture any plastic bags it may be packaged in) and it will outgas and become a harder ball. For at least one make of ball that is major market, the storage time before distribution is the only difference between two of their model names.
This is possibly a little off topic but are the DHS 3* ball off eBay anygood? Or should I avoid they seem very cheap, but I'm after some multiballs & don't want to spend a fortune.