In the spring of 2026 the Portland Shops produced an experimental vest-pocket class M that rode on the same compact trucks & 42" wheels that the class O vest-pocket J’s ride on. This design is intended for switching & branch line work where buckets of horsepower are not needed (they weigh 150 tons & produce 5600 HP) but the smaller 4-axle roadswitchers aren’t quite enough.

#1807 is operating on the PV&T’s branches in New England now, freeing a class K motor for operation elsewhere on the system.