All the changes and refinements made to the extremely successful model N were standardized and became the NA.  Low tension ignition was still used with a geared magneto now standard equipment with a battery and coil being an option.   They were offered in 3, 5, 7, 9, and 12hp with the 2 1/2hp being offered for a while before it became the 3hp NB.  The 1 1/2N was not offered as a NA since it became the 2hp NB.  The NA was not offered for very long, fully giving way to the NB in 1925.