1.6 Unusual American 5-receptacle NEMA 1-15 style outlet, ca. 1928
This is a very rare 5-way outlet from c. 1928, and is able to accept modern ungrounded polarized NEMA 1-15 plugs because the outlet is polarized. The outlet is still obsolete as the NEMA standard only provides for having at most 3 outlets from a single wallplate.
American 240 V "Australian" style
1.7 Left: American "Australian" style duplex outlet
Right: Compatibility of American and Australian 240 V plugs
The American electrical supply manufacturers Hubbell, Eagle, and possibly others made outlets and plugs that would match Australian plugs and socket-outlets exactly. These American outlets date back to at least 1915 (as seen in US NEMA 1-15 style 5-receptacle outlet Patent 1,179,728 filed in 1915), antedating the NEMA 5-15 outlets and plugs. They were meant for appliances requiring grounded 120 V, 15 A service, such as washing machines and gas dryers (to power the motor) for use in wet locations such as laundry rooms.
Split current/voltage ratings
Many older North American receptacles have two different current and voltage ratings, most commonly 10 A 250 V/15 A 125 V. This has to do with a peculiarity of the National Electrical Code from 1923 to the 1950s. Originally, receptacles were rated at 10 A 250 V, because the NEC limited lighting circuits to 10 A. In 1923, the code changed to allow lighting circuits NEMA 1-15 style 5-receptacle outlet to be fused at 15 A, but the previous 10 A rule still applied to circuits over 125 V. The higher voltages were rarely used for lighting and appliances. Most receptacles with this rating are of the "T-slot" type.