I need help deciphering crystal codes

[pandaemonium]

I come across a lot of crystals with peculiar codes on them like S33-55 and RK646000 are these standard code systems or are they vendor specific? also, often after a normal value you see another number e.g. 18.43-18, what is the last '18' for?
Any info or pointers would be great.

 

[zevon8]

I come across a lot of crystals with peculiar codes on them like S33-55 and RK646000 are these standard code systems or are they vendor specific?

- Not sure, maybe vendor specific.

also, often after a normal value you see another number e.g. 18.43-18, what is the last '18' for?
Any info or pointers would be great.

This is the "load capacitance" for the crystal. In this case, 18 picoFarad ( very common value BTW. ) This is the total value of capacitance the crystal will have placed across it when connected to the circuit. This is the value of capacitance required to have the crystal operate at its designed frequency.