555 50 duty cycle
E-design is right when using 4013 as this flip-flop will give you the perfect 50% duty cycle pulses, and avoiding using 555 as it can work for frequency up to 2 or 3 hundred thousand hertz only.
However, for the oscillator, to choose CMOS for working with crystal, the best device is 4069UB. In principle, any NAND or NOR can be used, but only 4069 will not make you troubled in any case. Consult 4069 datasheet for oscillation circuits.
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