They were a one or two year thing oldsmobile did. They fetch some money and yes they are rare but one problem with them is Oldsmobile stamped the letters into the valve covers and I'm assuming the die for the press wore out after stamping thousands of these and a lot of them ended up having a "faded" looking E at the end. The ones really that are rare IMO that may bring money are the ones with Clearer looking E's.