This came up on the AARoads Forum. NH 121A is currently marked as ending at the MA/NH line, with nothing on the MA side. SB, it's signed instead to end at NH 125 at the intersection north of the border on
Hazeltine Street. Signage from
SB NH 125 also says this, as does the
NB traffic light. Meanwhile, MA has a
MA 121A sign on MA 125 north at the intersection that continues currently marked NH 121A.
Just from what I've seen poking around in street view, I would assume that NH 121A should have its south end moved to NH 125 and that the MA sign is erroneous.