The fastest rotating pulsar: A strange star?

According to the observational limits on the radius and mass, PSR 1937+21 is probably a strange star, or some neutron star equations of state should be ruled out, if we alternatively suggest that a dipole magnetic field (rather than a quadrupole one) is relevant to its radio emission. It is conjectured that PSR 1937+21 and PSR 1257+12 (and possibly some or all of the isolated millisecond pulsars) may have weaker dynamo-originated magnetic field due to a less effective field magnification process