Seen on eBay: a prototype of an iMac (well, a motherboard, actually) with a particularity, an Nvidia graphics card.
Under El Capitan
The motherboard has diagnostic connectors that are not found on the standard version, naturally, as well as an Nvidia graphics card based on GF108 (an entry-level chip). The name indicated on the captures is GeForce GT540M with 512MB of video memory. The seller indicates that the EFI does not contain the code to initialize the card before macOS starts up.
Some diagnostic ports
The motherboard
The GPU
The author is apparently asking for a quite high price: at €75, the reserve price has not been reached at the time of writing these lines.
