Before this question can be answered ,you will need to include if this Walther p-38 is a wartime production model(with Nazi proof marks),or if you have a civilian model made after World War II.
You will need to contact Walther to find out.
1961
Dieter Marschall's book on Walther has sn data in it.
Try asking on the p38forum.com
Try the P38forum
Someone at the p38forum.com will probably be able to help you.
Someone at the P38forum.com should be able to help
You will have to find a copy of Dieter Marschall's book.
Someone at P38forum.com might be able to assist you.
Double check your weapon. Your sn does not appear to have enough digits.
5000$
The Walther P38 with a serial number 6660 was likely made in 1940. The P38 was produced during World War II, and early production years can be identified through their serial numbers. However, for precise dating, additional information such as the manufacturing code and proof marks would be useful.