Siemens E188CC / Cca Date Coding

Can anyone tell me how to translate the date codes on Siemens E188CC and Cca tubes? I want to shop for a good pair from the early 60's but I'm not sure of how I can identify them positively.

Need help!

Check Brente Jesses website I think he lists the German codes, I know the Phillips Mullard codes are there.
If you want a Siemens CCa I hope you got a good rate on your second mortage.