The administration of the retirement system established by this chapter is hereby vested in the board of trustees established by N.H. Rev. Stat. § 100-A:14 and it shall have with respect to this system all the rights, powers, duties, restrictions, and immunities it has with respect to the retirement system established by N.H. Rev. Stat. Chapter 100-A and the word “board” or phrase “retirement board” when used in this chapter, unless a different meaning is plainly required by the context, shall mean said board of trustees.