Abstract: An electrically driven stepmotor valve assembly including separable annular stator and rotor-valve assemblies. The rotor-like assembly having a cylindrical housing adapted to slip fit inside a central, domed, stator cavity, with alignable locking members on these assemblies permitting rotary interlocking upon the slip fit assembly thereof. A sealing arrangement, in the vicinity of the open end of the stator assembly, peripherally seals the stator and rotor-valve assemblies relative to each other, when assembled, with the rotor housing having a locating plate ring portion which, in turn, supports an elastic sealing member that fits into a groove in a bottom wall of the stator housing. A plurality of differing sealing arrangement designs and structures, including sealing member reinforcing structures, are set forth for the sealing of the interlocked stator and rotor-valve assemblies relative to each other.