Here are some vintage receptacles that I found today:
The outlets above from left to right are:
a Bryant "Twist Tite", 10A 250V or 15A 125V,
a Bell GFCI, Class A, Group 1, 15A 125V 60Hz (Co/ALR),
and Hubbell, 10A 250V or 15A 125V.
In case you can't see it, the bottom plug on the Hubbell is an ungrounded T slot. Does anyone know how old the other two are or come across them? I remember Square D had a GFCI like that Bell in the 1970s.