Any member who works one hour or more after his or her assets are transferred to the state Teachers Retirement System pursuant to this article is subject to the vesting schedule set forth in article seven-a of this chapter: Provided, That if a member is vested under the Teachers' Defined Contribution Retirement System and his or her last contribution was not made to the state Teachers Retirement System, that member is subject to the vesting schedule set forth in article seven-b of this chapter.