  We propose a method to determine the mass and spin of primordial black holes
based on measuring the energy and emission rate at the dipolar and quadrupolar
peaks in the primary photon Hawking spectrum, applicable for dimensionless spin
parameters $\tilde{a}\gtrsim 0.6$. In particular, we show that the ratio
between the energies of the two peaks is only a function of the black hole
spin, while the ratio between their emission rates depends also on the
line-of-sight inclination. The black hole mass and distance from the Earth may
then be inferred from the absolute values of the peak energies and emission
rates. This method is relevant for primordial black holes born with large spin
parameters that are presently still in the early stages of their evaporation
process.
