It looks odd. We can't identify what it is by date (There's no date! I've never seen IBM do that!). However, it has drainage holes, so it could be from the 90s... But the connector is identical to the 4704 style boards. The case almost looks like plastic, but it also comes with it's box, so it could just be kept VERY well.
The keys are molded to their respective rows, another hint that it's not buckling spring (although it could be very early buckling spring with a flat capacitive PCB). It has a combination of spherical caps and caps like what would be found on a buckling spring board...
And now for crazy hypothesis time! I'm betting on pre 4704, so pre 1983. It's a transition between beam spring and buckling spring (flat capacitive PCB, but with buckling spring and spherical keycaps for the main molded). It set the case design for the 4704 boards, but not yet the built in curve that IBM put into their keyboards later on. Let's go all the way and guess for double shot PBT caps (they are more likely dyed).
