Reading the code on a crystal oscillator

I have found a crystal oscillator lying around, but I have no idea of its resonant frequency. There are some coding on the oscillator reading "S661", as shown in the figure, but I have no idea of how to read that code. It would be great to hear some tips. Thanks. Btw, I am having a hard time finding a guide of reading such code on the internet.
**broken link removed**

That type of code was probably a manufactor specific marking, without knowing the maker there's not much of a chance of you decoding it, most crystals have their actual frequency printed directly on them. Only way to tell it's frequency is to build an oscilator with it and find out what it starts up at.

Based on size, most likely a 32.768 kHz watch crystal.