I know these pics aren't the greatest...the wife has the Nikon, and a scan will work for this. Have found different mintmark placement on some 1956d Lincolns. One is almost into the date, the other looks to be a normal placement. Is this a variety I don't know about, or just normal mint workings? They don't seem to be OMM.... This one looks to be 'normal'... This one is almost into the date...
Before 1990, the mm was inserted by hand, and wanders around depending on the accuracy of the striker. I have a few that seem to touch the date, but as long as they are in the area under the date, and between the bust and the rim, they seem to have little premium. Jim
Although I should add, they do appear on ebay occasionally with a buy it now of many thousands, saying that they are an enormous error....etc...etc. Jim