Contax T3 double tooth

Hi guys,

I'm very serious about purchasing a Contax T3. I understand the later ones came with two sprocket teeth on the take up spool, hence the nickname "double tooth". The thing is, I don't know when that was introduced. Is there a minimum serial number that I should be looking out for?

Also, there is a black variant - were they available from the beginning, and if not, will they have the double teeth?

Thanks in advance.