I guess the point is, if there is no other damage to the case, then it can easily be de-yellowed to near new condition. Then it can be sold. I've got nothing against borrowing parts from one to the other, but then it comes to dismantling irreplaceable parts on a 128K and 512K, like fly-backs, custom ICs and such, I much prefer to buy a cheap, preferably damaged Mac Plus, which were so popular that it will be years before they become endangered. Not only are the parts more robust, but there's an ample supply, and 100% interchangeable. And a nicely restored 512K will probably fetch enough on eBay to pay for the Plus with a nice profit left over. Obviously when it comes to restoring a 128K and 512K to original condition using original parts, then some 128K and 512K will have to be sacrificed - but hopefully it will be one with an unrestorable case, with cracks. Yellowing can be fixed now, or at least it's worth a shot before designating it for the landfill.