Hmm...interesting indeed. We learned a while ago you can't go by the date on the box either, so here's a basic list of the revisions:
r2- Plastic cup, hard plastic filler ring
r3- Ceramic cup, no black shrink wrap
r3.5 aka 'bastomizers'- Some came w/ filler installed, etc
r4- Black shrink wrap around cup
r5- Factory never recognized this number but vendors were applying this to the clearomizers
r6- Fat wicks, Martinez himself called these r6 to a supplier
I think it's important to think of the metal and clears as two different lines in a sense...
Also, many vendors didn't put r5 on their websites because they got reports that some of the boxes had a mixture of the old and new wick styles...or no new fat wicks at all.
My r5 clearos and metals both had fat wicks...both were supposedly pre-burned or otherwise guranteed that they had not used the 'funky anti-bacteria chem' in them.
I think r6 is for clearos with fat wicks and thicker plastic on the clearo sleeves.
Two more batches past r5/6, no idea what they call them...
The black jacket on the ceramic cup doesn't go as far up anymore...so the wicks don't get squished or pinched against the sleeves as much.
They now send metal syringe needles in the box instead of those flimsy nylon ones.