For the #2, #3, and #4 it's quicker to look for the various unique markers than for the RPM itself as all are fairly subtle and require the right lighting angles to see them well. Die cracks and chips in the date and such pop out. Of course if you only look for these things you may miss an EDS example of the RPM, so you have to do both. I usually take 3 or more passes through any roll to make sure I didn't miss anything, and look for different things each pass.
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