I did notice what looked like a bit of yellowing on the front of the case compared to the rest of it. Is that the case or is that how it normally looked?

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The rear case bucket is ether not original to that computer or it has been cleaned and they have not touched the front of the unit. It is highly possible that the computer was upgraded and has recently been downgraded again prior to sale. Many original 128s were upgraded later to Macintosh Plus status with the new rear case section.