Serial number 540394 dates production to 1967 (production ceased in 1971). NOTE : The spring on the locking pin for the clearing ruing is weak. It does not lock the ring. The ramification of this is that to clear anticlockwise you push the folded locking ring anticlockwise rather that have it extended. If you want a'perfect' Curta then this may be an irritant but it does not affect the functionality of the machine.
The calculator comes with a copy of the instruction manual and an article from'Scientific American'. Dimensions: 6.5cm diameter x 11cm high. Condition: Excellent (appears very little used). Please examine photographs for condition.