checked exchange markets on page 1.
Maybe some mistakes.
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Exchanges

        www.ecoinfund.com -> down
        www.comkort.com   ->  working, but not that much valid history
        www.europex.eu      -> working, valid buy&sell orders and trade history
        www.coinano.com    -> no GMC page
        www.allcrypt.com     -> working, but no valid trade history confirmed
        www.cryptokk.com   -> down?


To me, looks like europex.eu is the most valid exchange market for GMC at this moment