Middlesex County Retirement Board, East Cambridge, Mass., hired its first currency managers, A.G. Bissett and Cambridge Financial, to manage $70 million. The move was made for diversification in the wake of a recent asset allocation study, said Nancy ONeil, investment coordinator for the $540 million fund. The move will be completed Wednesday. Each manager is slated to run about $35 million. Cambridge Financial will do currency overlay for three of the funds developed markets managers. A.G. Bissett will also do currency overlay for three managers, both in developed and emerging markets, said Gus Aristizabal, COO of Wainwright Investment Counsel, the funds consultant.