Vintage and from the same estate sale.  Gotta love these old trick pocket knives.  Harder to find than other lock types.  Rotate the knife changes the pin position which locks/unlocks the blade.
 
Cream colored mother of pearl handle pocket knife.  Made by Imperial in the USA from 1956-1988.
 
Condition:  Works as it should.  Scales have no cracks or chips.  Doesnt look like it was used much.
 
3" when closed.
 
Location D2-22