I do have the approx date but not to hand.
A couple things to add which I am sure you wil recall (when you first posted I think these came in a second post).

The compound of the chips themselves was changed, to a harder material, and the process of smoothing the edges was stopped (to save money).
The new chips were made in a different location using different molds.

BTW - we are both agreeing with Mr Lueders. That's unusual