Expanding dead outlet problem
House is in Minnesota, built in 1911. Unfortunately I don't have any idea on the wiring; neither the previous owners nor the city had any records. I'm assuming "newer than 1911", if only because they're normal 3-prong outlets, but that's still a pretty big window of time.
I tested all the 3-prongs in the house when I moved in with a plug-in circuit tester (primarily to make sure they were all actually grounded) and both outlets in question tested correct.
Tidbits that may or may not be helpful to estimate wiring age:
* The city did have a record of panel upgrade to 100amp service, ~1955
* I was replacing a 2-prong with a GFCI (months ago, separate circuit) and discovered there was actually a ground wire; it just wasn't hooked up to anything. White, black, and bare were all in the same sheath.