You will need to contact Walther to find out.
1961
http://www.p38forum.com/
Dieter Marschall's book on Walther has sn data in it.
Try asking on the p38forum.com
5000$
Try the P38forum
Military P38s are dated from a 3 letter code, and not a serial number.
Someone at the p38forum.com will probably be able to help you.
Someone at the P38forum.com should be able to help
Someone at P38forum.com might be able to assist you.
You will have to find a copy of Dieter Marschall's book.