  Massless elementary-particle propagation is represented historically
(cosmologically) through 3-scale ``towers of quartet rings'' within a lattice
of magneto-electrodynamically communicating ``pre-events''. The lightlike
intervals within a ring of 4 pre-events (discrete ``closed string'') display
transverse GUT-scale and longitudinal ``particle scale''. The lightlike
(longitudinal) spacing between successive rings of a tower is at Planck scale.
Ratio between GUT scale and Planck scale relates quantum-dynamically to
elementary magnetic charge. Permutations of a ring quartet, in conjunction with
Lorentz-group representations, control elementary-particle quantum numbers.
