Steve,
The only way I could tell you the manufacturing date from the serial number would be to have Germany look it up. I looked at my CT 22 and there's a date on the same label holding the serial number and other information in the form of 05/06, meaning it was built in May of 2006.
I don't have a MIDI here at my house, but it may be worth checking again.
PS - Are you sure it's the manufacturing date you need or is it the purchase date, which is what the warranty is based upon.
Shane