    function contractApprovedBoth(address traderAddr1, address traderAddr2) external view returns (bool) {
        if (exchangeContractVersion > 1) {
            return
              exchangeContractVersion == traderApprovals[traderAddr1] &&
              exchangeContractVersion == traderApprovals[traderAddr2];
        } else {
            return exchangeContractVersion == 1;
        }
    }