Most of them have something wrong with them now, faceplate, key membrane, caps, voltage regulator, memory chips .. been looking on Ebay but a lot of sellers think they are sitting on gold without realising that to fix these up properly costs £££
If the faceplate is beyond touch-up repair then it may need a new one which sell at around £20 which would greatly affect what I'd pay tbh, give it a test and throw some pics up and I'll tell you what I think.