From what I understand, Groestlcoin has to be bought with bitcoin. Coinbase is a sort of bank or holding company which accounts can be maintained and if a person wishes to have their crypto currency stored there they also do that.
So it appears that TAUG set up an account with Coinbase to buy the currency needed to purchase Groestlcoin.
No different than say going to a bank to exchange dollars for travelers checks.
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