Google AdWords My Client Centre
https://adwords.google.co.uk/support/bin/answer.py?answer=7725&topic=1163
In response to advertiser feedback, Google AdWords offers a powerful tool for handling multiple AdWords accounts: My Client Centre (MCC).
MCC allows support for large advertisers with multiple AdWords accounts and third-party agencies, such as search engine marketers (SEMs), search engine optimisers (SEOs), and automated bid managers (ABMs), who manage and optimise multiple AdWords accounts.