Something quite rare on eBay: a development Pippin. It’s not really a prototype, but a model used for game development. It probably (though not certainly) contains a ROM that allows booting from a hard drive.
In terms of differences from a regular Pippin, aside from a few stickers, you can note the lack of markings on the front (no Pippin, PowerPC logos, etc.) and on the back (no product number). The console, sold without a controller, is however equipped with a SCSI ribbon cable. Well, it’s still expensive.