(Sharecast News) - Spectra Systems signed a five-year contract extension worth a minimum of £3.2m with an existing optical materials customer.The AIM traded banknote authentication specialist said the contract, which commences in April next year, is with one of the largest suppliers of security inks for the banknote industry.Nabil Lawandy, chief executive of Spectra, said: "We are delighted to have executed this contract which secures the use of our phoshour materials in some of the world's leading banknotes. This contract, along with other recent service and sensor development contracts further underpins our revenues and earnings visibility going forward."Spectra Systems' shares were up 5.38% at 137.00p at 1342 BST.