1958-D RPM Again I Can't Find In RPM Guide. Maybe Because It's Not A RPM? Help

As far as I know, the main use for markers is to verify die state/stage.

Many people reference die markers trying to show that they have a variety but, that is backwards. Always the variety then the markers.

1.Die scratches are added to a polished die.
2. Die scratches in the open fields can fade with the striking process.
3. Die scratches near a device last longer.
4. Die scratches inside of the device, lasts the longest.
5. Die polishing will remove flow lines, clash marks, Feeder Finger Damage. Leaving the fields looking clear without the flow lines,
6. Each time the die is polished, while it makes the fields look nicer, the devices will get smaller in height and width because of the field reduction.
7. After the second polishing, the devices tends to show more die wear.
8. Aft the third polishing the devices show even more distortion and you start to see more die cracks and chips. These can happen earlier if die clashes another die events happen.
9. When the dies are polished for the 4th time, they make a call to either retire the die, or polish the die knowing it is in the VLDS die state. This rescue will show the most extreme die wear and the smallest devices sizes. So this is the final chance for a die to be polished, or retired. Note on these images you see the affect of strong flow lines around the eyes, the die cracks are there. The extreme die wear on the ONE CENT areas in the last sets of image. So any previous die scratches on the earlier die states are now gone. New markers will appear.
10. Thus depending on the mint placement, the die is a listed one or not. The only thing that doesn't change on a pre-1990 coins. The dies can experience different events that can fast track the polishing of coins, or sometimes a different die is replaced by a damage die, forming a new die marriage.

CoopHome: How are Dies affected by die polishing?

Here are the side by sides as promised:
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It is die RPM-018
1958D-1MM-018.
Not RPM-048

Not sure what you are looking at that brings you to that conclusion because your chart indicates it is not RPM-18.
The big gap [crescent] that is created inside the 9 with the yellow line makes it obvious: The gap on the OP's coin is much smaller.

A better way to compare is with overlays. Not perfect, but better. I don't think your matrix is configured correctly.

BTW: there is no RPM-48 [only 1MM-48].

Nice job, CentSation. coop, both of your vertical lines are much further west than grospoisson's. This may be why you aren't seeing the match.

Not familiar with this method but, I believe that the correct way would be to switch the two middle pics* then redraw the verticals.

* not have the OPs pics set as three-in-a-row, vertically - only top and bottom.

It is a RPM-18, not a 1958D-1MM-048. The mintmark location for the 048 is too far east.

"It is a RPM-18..."

Ummm, no it isn't.

edit: thanks for the graphic makecents, I am too tired to deal with the 300k limitation on pics and the switch to the different image optimizer