I don't know a lot about error coins, but I saw this eBay seller listing two Lincoln pennies while I was searching for large cents (why he has them miscategorized is a question for another day). Anyway, he claims they are missing words, but if you look at the coins it is obvious they have either been sanded or had some chemical applied or some other process. It looks really blatant to me. Do you agree this looks fishy? http://cgi.ebay.com/BU-1969-S-ERROR...33?pt=Coins_US_Individual&hash=item1c17a4eb71 http://cgi.ebay.com/BU-1971-S-ERROR...55?pt=Coins_US_Individual&hash=item1c17a4eb87
I used to do some copper etching with acid back in HS, kinda looks similar, with just a felt pen and some HCL you can achieve results like that.
Hard to tell from the pics, but they could be struck through errors (struck through grease or debris).
There's all sorts of things that can go wrong during the minting process - some of them are valuable, like a doubled die - and some of them not so much, like a grease filled die or a rotated reverse. I'd put both of these in the second category of not so valuable strike issues. The first one might actually be PMD.
I was thinking that one looks like a struck-thru debris I have. Not worth a premium, and definitely the $3.75 in shipping.