There is another confirmed platinum 512Ke belonging to a forum member. It's owned by macdownunder and was discussed in a thread called "Complete Collection of Every Compact Mac" in 2007. There is a link to the picture in that thread, but it appears to be down right now. The photo had four Macs in a row--a beige 512Ke, a platinum 512Ke, a beige Plus, and a platinum Plus.

The page of the thread with the link is here:

viewtopic.php?f=7&t=334&start=50

I don't believe he had the box for it, so while it may not answer our box question, it does show two things:

1. The platinum 512Ke from the auction is not an anomaly.

2. These machines were distributed to Australia (unless he had it imported from another country).

I thought of something we may wish to try. Check your local libraries to see if they have any Macintosh-related magazines from 1987. Look at the articles and the ads to see if there is any mention of the 512Ke either being offered only to education (which would explain the lack of Mac EDs in the US) or if there were any offered for sale to general computers that weren't closeouts. In particular, a summer 1987 issue would have a platinum 512Ke on sale somewhere in the ad section. If it's not there, it wasn't a general public offering.