1961P Nickel - DDO or DDD  

 

You have the term right, it is a bit of DDO. The letter tops have moved real close to the very edge of the die with metal flow. Here is a diagram, for a different die problem on the nickel but this depicts what a die looks like. it is slightly rounded. On the edge is an area called the rim offset, makes the rim (think reverse on all this). With metal expanding, the die enlarges and must be trimmed down to fit it's housing. the rim offset is re-milled but this cuts inwards into the design elements, hence here, the letter tops get whacked off. OK?