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

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