  We revisit the pointer-based measurement concept of von Neumann which allows
us to model a quantum counterpart of the classical time-of-flight (ToF)
momentum. Our approach is based on the Hamiltonian for a particle interacting
with two quantum pointers serving as basic measurement devices. The
corresponding dynamics leads to a pointer-based ToF observable for the
operational momentum of the particle. We can consider single measurements of
our quantum pointers and show that this process will result in a state
reduction for a single particle being downstream of the time-of-flight setup.
