Is the unused meter base newer than the meter base that feed the 100A panel? If so, then maybe the whole transfer to the new panel and base got aborted due to routing of the power to the new meter base and 200A panel. You gotta look at that... an aerial run may not work and an underground route may cut the driveway or septic field or something. You should not be routing that power feed through the house, as there is no breaker in line to protect it in case it shorts.
