Boston's top financial official announced her resignation Wednesday after 16 years in the Menino administration, during which she won high marks for her prudence, toughness, and guidance of the city through the nation's worst economic crisis since the Great Depression. Lisa Calise Signori will cede control of the city's $2.3 billion budget next month to take on a new and potentially less political challenge: becoming chief financial officer of the Perkins School for the Blind. Founded in 1829, the institution famously taught Helen Keller, inspired writings of Charles Dickens, and rejected a job application from Henry David Thoreau, who apparently did not share Signori's affinity for math. At Perkins, Signori will manage a $65 million annual budget that reaches into 64 countries and serves 115,000 people across the globe, from its main campus in Watertown to manufacturing plants in India and South Africa, where it produces Braille materials. Signori spent time at Perkins as a child, when her aunt was a student there, and has been looking for opportunities in the nonprofit world. 'This is about my longtime passion,' Signori said in an interview Wednesday, after announcing her departure at the mayor's weekly Cabinet meeting. 'This has nothing to do with the City of Boston. I'm quite proud of working with the Menino administration.' The city is actively seeking a replacement for Signori, whose formal title is director of administration and finance, according to Dot Joyce, spokeswoman for Mayor Thomas M. Menino. Signori's departure will leave a significant gap in Menino's Cabinet. With her forceful personality and a ubiquitous Hewlett-Packard business calculator that she carried like a BlackBerry, Signori tightly controlled the city's purse strings. 'I think she served as an excellent steward of the city's finances during the good times and the not-so-good times, the two recessions,' said Samuel R. Tyler, president of the Boston Municipal Research Bureau, a business-funded city watchdog. 'She did a good job of protecting basic services at a time of cutbacks, and I think some of the steps taken over the last few years put the city in a better position in the future.' Signori managed the city's books so well, in fact, that the firefighters' union used her skills against her in its epic, four-year contract dispute with Menino and his administration. The union argued that Signori's financial stewardship was so steady through the recent economic meltdown that the city had more than enough money to pay for the raises outlined in a controversial arbitration award. 'She was a tough opponent at the bargaining table, but I respect her as a professional and wish her well,' said Edward A. Kelly, president of International Association of Fire Firefighters Local 718. During Signori's tenure, the city achieved its highest bond rating ever and implemented a data-driven performance management system known as Boston About Results, or BAR. She became a zealot about the need to rein in the rising cost of municipal health care, though some criticized Menino's administration for not being tough enough with unions. The diminutive woman in glasses could often be seen lugging oversized charts around City Hall, carrying poster boards with pie graphs depicting revenue and expenditures. She was known to wield a nearly photographic memory for obscure figures. In a statement released Wednesday, Menino spoke of her 'sharp intelligence and dedicated work ethic.' 'Lisa has been tremendous for this city,' Menino said. 'Perkins presents a once-in-a-lifetime opportunity for her to pursue a second passion, education, and I know she will be successful.' A native of Somerset, Signori earned a bachelor's degree in economics from Boston College and a master's degree in public management from the University of Maryland. Hired by the city in 1994, she became budget director in 1998, chief financial officer in 2003, and director of administration and finance in 2007. Signori's last day at City Hall will be Sept. 15, and she is scheduled to start at Perkins at the end of that month. 'Lisa's skill, both with numbers and with people, her passion, and her compassion will make an impact,' said Steven M. Rothstein, president of the Perkins School for the Blind. 'Whether it be the 600 babies in Massachusetts we see every year who are blind or the thousands in Boston alone who we serve with Perkins Braille and talking book library, she will help us to make sure we are reaching them efficiently.' 