un converted one would id assume whenever ive had robot pets ive found them hard to trade if they don't have the casings they aren't worth much with casings id think you could get maybe 5$ from a popular robot pet, but ive found them hard to sell when ive had them
Unconverted pets are neopets that have the old neopet art, they are very rare and worth a lot casings is the 'outer cover' of robot pets robot pets are rather cheap in the BM
Well, on the Pound Chat, robot pets are not worth much really. You can generally get a WNed popular basic LE (hissi, cybunny, poogle) to a well named baby pet. The value of robot pets do vary hugely depending on the species- robot hissis can go for royal custom (so sell for 1.75 million) but something like a robot acara would be lucky to fetch a baby. Uncovereted pets came about from the 'great conversion' a few years back. Most pets auto convereted to the new art, but some, the ones who's art changed more radically, got the choice to remain as they were. There were the UC pets. Lots of people chose to convert though, which is another reason for their rarity.
Have a look at the list of Robot Neopets by googling it. (Would link however not sure if it's allowed) The Robots have casings also that are basically wearable items that make it look slightly different.