plenty of difference the ppks is a shortened version of the walther pp - it is not a ppk - thanks to stupid govt regulations
Take it to a professional who specializes in air weapons.
100-1000 USD depending on specifics
100-1000 without more information.
100-1000 or so
There were two companies known as Interarms. The first was an importer/exporter, formed in 1953. They did not manufacture firearms. The second - and current - Interarms is a subsidiary of Hi Standard, and does not manufacture a PPK or PPK/S pistol. If what you have is actually a Walther PPK/S, value could range anywhere from $300 - $800, depending on specifics.
The PPK/s is a PP with a PPK slide.
1969-1984
no published sn data.
Someone on the P38forum.com might have access to that kind of data.
You might have better luck on P38forum.com
It's not designed to do so. (No.)