"Cheater" plugs
These will only provide a ground if the box is grounded, such as if the house is wired with metal conduit, armored cable (BX), or NM cable with a ground wire. Many older homes are wired with non-metallic cable such as 14-2, that has no ground.
The house I'm currently living in was built in 1938, and most of the system is not grounded. It's new enough to have NM cable instead of knob & tube. Newer circuits have been added for electric heat, window air cond., and refrigerator, that are all grounded. I plug things such as computer and vacuum cleaner into either the air cond. or refrigerator outlets, and have no trouble. The house has a newer 200A breaker panel though it is a small house. There are some old fuse boxes in the basement for the dryer (unused), water heater and a couple other basement circuits.
I'm surprised fuses were used in some homes built as late as the 60's, as circuit breakers have been around for many years. I have a 1939 Westinghouse catalog that shows various sizes of circuit breaker panels, and I'm sure many other companies made them as well. My own house was built in '52, and had a 100A fused service until my dad had a 200A breaker box installed in '73 when we got central air. My grandfather's house, a small 4 rm. Mississippi shack, had circuit breakers from when it was first wired in '48. I always though that made it more "modern" than our own house.
Another variation I've seen was a fused panel that has switches next to each fuse. The middle school I attended had such a setup. Though the building dated from the turn of the century, the wiring had been updated circa 1950.