MARBLEHEAD-Selectmen have extended their deadline for prospective members of the Conservation Commission so that interested people can find out first-hand what the commission does.Selectmen originally wanted letters of interest submitted by 5 p.m. Dec. 12, but as Selectman Judy Jacobi pointed out last week, the commission’s next meeting is Dec. 13.Board members unanimously moved the deadline up to Dec. 18 at 5 p.m.Letters should be submitted to the Board of Selectmen, Abbot Hall, 188 Washington St., Marblehead, MA 01945.Town Engineer Doug Saal informed selectmen a month ago that the commission was seeking individuals to fill vacant seats. The commission has one opening at present and anticipates another by Jan. 6."There are three people interested and they want to go to the commission meeting Dec. 13," Jacobi said.Two of the three are Marblehead native Mark Brings, a contractor, and Brian Leclair, a lawyer and former director and president of the Cambridge Civic Association.They were among the four applicants for seats on the Planning Board. They did not receive enough votes for election but selectmen urged them to consider applying for the Conservation Commission.Brings has volunteered at the Coffin School and veterans’ groups and told the board he wants to see the town pull together, and Leclair moved to Marblehead after what he described as a life-changing experience aboard a New York shuttle flight the morning of Sept. 11.Meanwhile board members are also seeking applicants for the Finance Committee, which has six of its nine-member complement as it prepares to work on the Fiscal 2009 budget, and the Historical Commission, where Elizabeth McKinnon has resigned.The deadline for letters of interest for the Historical Commission seat is Wednesday, Dec. 12, at 5 p.m.