Thanks Richard,
You're right 508 is a single mirror. 732 is the soft top colour, dark grey.
The hardtop seems to be a later addition as it's a 280SL type with coarse grain vinyl and lacking the built in locking handles of the 230SL. I wonder if the owner of this 230SL might have later ordered the hardtop? I wouldn't have thought MB would stamp the body number in a hardtop ordered that way, but I can't account for the correct body number otherwise. Good thinking on the hubcap colour; I only have one original hubcap and it's gray, no red beneath.
Although gray with red tex is not listed in the standard exterior/interior combinations, almost all the graphite gray cars I've seen have a red interior.