Hello mixchaxx,
maybe this info is helpful.
I have changed from Surface Pro (Gen.5) to Surface Pro 9.
The old keyboard had 6 contacts in the centre, the new one has 6 very small contacts on the right centring cam.
I can't connect the old pen to Surface Pro 9.
The new pen has no batteries, but a rechargeable battery that is charged in the storage compartment of the keyboard.