I think that that is mechanical/machine doubling. It's pretty common and not worth much of a price increase, if at all.
MD is when the coin gets a little loose in the holder, however minor. In the millisecond after the good strike, the die will move a little in one direction or rotation as the die rises up off the planchet. It will leave what is called a shadow or shelf-like image of the design on one side of it. Depending on how loose you can get a good shadow/shelf, but sometimes just a little. Once a worker tightens the holder, no more MD. On some dates/denominations it's not uncommon
1969-S DDO does not have doubling on the mintmark. At that time mint marks were applied to working dies not hubs.
That goes with all coins made before 1989. If the MM shows the same doubling as any part of the rest of the coin, you can guarantee that it happened during the striking process.
The doubling on the 1969-S DD (the rare, valuable one) is quite dramatic and easily seen with the naked eye.
