Garry, I was looking through an original 230SL brochure which has pictures of an early 230SL (round steering wheel so 1963 or early 1964). The picture of the engine bay shows the blue sticker on the brake booster in the same location and orientation as that in your second picture of your original post.
Interestingly, the picture also shows four of those rubber rubber strips along the ridge at the top of the fire wall rather than three which i think most people have, including myself (since they line up with the three bumps on the hood).