Oct 11 (Reuters) - Cryptocurrency trading firm Copper.co said on Monday former British finance minister Philip Hammond has joined it as a senior adviser to help with strategy as the London-based company expands its global footprint. Copper.co provides tools and services to acquire, trade, and store cryptocurrencies. The company completed an extended $75 million funding round in June, led by investor Alan Howard, and venture capital firms  Dawn Capital and Target Global.    "Over the last 18 months, Copper has grown exponentially, now serving over  400 institutional clients ... With Lord Hammond"s expertise adding to the strength of our team, we look forward to growing Copper," said Chief Executive Officer Dmitry Tokarev.