1960 D Penny DDO And RPM?

The MM looks to have the split serifs, but there are quite a few known examples to choose from.
I don't think WRPM-051 is a match. Also not seeing a DDR.

This is a nice RPM, but there are 113 of them listed on VV alone. See if you can match it up to one of them, Far too many for me to sort through at the moment.

Focus on the Small Date's and the RPM's position. That narrows it down a good bit. Thanks, Doug.

Pay attention to what Halo1st told you, your mm is not even close to the one you suggested. Something I will do starting out, is use VV's listings. They have the full date and mm shown, you don't even have to open up each listing, this way and you can narrow it down quickly. I will usually crop a nice pic of the date and mm, making sure it's oriented the way VV's dates are (all the listings are usually oriented in a very similar way), open up VV's listings and then have my cropped date mm off to the side. I can usually narrow it down in just a few minutes, if it's an unusual mm location, I can find it in less than a minute. Give this a try and see if it helps. I use all three sites but always start with VV on RPM's because of this.

Here's a pic to explain what I'm talking about.