Lionel used the Pennsy J1 boiler for their model of the C&O T1. On the real T1, the boxy sand dome sat near the middle of the boiler with the steam dome ahead of it. The whistle was mounted on this steam dome.
On the Lionel model (shown here behind the Pennsy) there is the same large combination sand/steam dome that PRR used. The steam dome is hidden by the housing of the sand dome. The whistle is mounted behind this combo dome.
The only 3-rail C&O 2-10-4 with a correct boiler was released by 3rd Rail.