A certificate from the applicant and/or developer, signed by the Town Clerk certifying that cash in an escrow account, or certified check, bond or other acceptable security or combination thereof, payable to the Mayor and Town Council of Oakland and satisfactory thereto in form, sufficiency and legal execution, has been filed with the Town Clerk. The form of such escrow account, bond, certified check or other acceptable securities shall specify the time for the completion of the required improvements, and shall provide that, when the improvements have been completed and approved by the Town, the guarantee shall be released and returned; it may also provide that as the required improvements progress and are approved by the Town, a portion of the bond, monies or other security commensurate with the cost of the improvement may be released and returned to the applicant; or