how common are "burned outlets" that are old?
Exterior outlets on a home this old may be more recent additions and still be older than the code requirement for GFCI's. I would power down the circuit pull the outlets and inspect the wiring. With external outlets that are not sealed and have "in use" covers or "extra duty" covers water gets in the outlets and they corrode. The in use covers have a cover that allows the outlet to be used while keeping rain out. If all the outlets are on 1 circuit you may find one has failed and the others are daisy chained, not receiving power from the point of failure. The other possibility is, I used to install switches on exterior outlets to allow holiday lighting to be turned off (there may be a switch some place that has killed the power to them).