History shows that the final look of the Macintosh was in beige, and thus the translucent case is considered a rarity. The material allowed people to see the innards of the computer, including the CRT monitor, circuit board and others.
The casing also showed how there was a lot of space in the rear area and along the curve. @DongleBookPro has not divulged any other information, but it’s common practice in Apple to make their prototypes in transparent cases, which was what happened to the M5120 or Apple Newton.
If the Macintosh Classic would ever appear in the auction it will be considered rare and typically fetch a huge amount.
@DongleBookPro regularly puts up prototypes and unreleased Apple devices on social media. Some of the items shared are a first gen Mac mini and a first gen iPod touch prototype.