I have a similar one which luckily survived the winter in the greenhouse, being warmer in there than the house over spring and summer it had it's first flower this year. The flower bud looked much like this, the plant is similar too. The label in the pot says Gymnocal, so I guess it's Gymnocalycium. The flower was huge and scented but only lasted a day, I had brought it inside to capture it.
http://www.llifle.com/Encyclop...
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