This is one of those anomolies that came out of the Gillette factory and now 60-odd years later, we are left wondering where did that come from!.
It's a Slim but has a Super Adjustable base plate.

How does it shave?
I still have to use it, however I suspect that without a shave-off I'm not going to be able to tell the difference between it and a Super Adjustable 84.

Slim vs Slim SA Hybrid vs Super Adjustable 84
The image and table below is a summary of the similarities and differences.
The immediate different base plate can be seen in the image. Also take note of the font that Gillette used for it - its the same as the Slim.
The base plate and center bar / side plate pieces are the same as the Super Adjustable, however they were changed during the Slim manufacturing era.
The doors and middle plate could be from either - Looking at them I don't think that Gillette changed those two parts. The handle is "Slim".
It's numbered N3, so 3^rd Quarter of 1968 which was the second last quarter of the Slim razor and the 1^st quarter of the Super Adjustable 84.