I vaguely remembered there was a change in the center tray.
In the tech manual you have access to the Pagoda Notes that list the changes through the years.
In Pagoda Notes Volume 9 No.3 - The center box was changed with 230 SL VIN ending in 771. The ashtray was added. So an early box, would be just that, a rectangular box. Fitting the cut out with the circle would probably have been an easy modification. They did not come from the factory that way.
Does look like nice work, and probably quite useable.