The 2006 .....I looked at it very close under 10× and no indication of grinding, sanding or polishing. 2013 has impression in it , might be a vise job?
The 2006 is just worn down, probably intentionally. The 2013 has been damaged by heat causing the layers to bubble and separate.
No indication of it being heated, would have discolored, pic not that great but it looks like something was pressed into it, except all of the details th as should have been pressed flat are still there.also as you can see 2 different impressions, they don't go thru to other sides, nor line up with each other
Definitely heat damage, seen it many times. Not necessarily any discoloration, depends on the heat source. It could also have worn down afterwards eliminating any discoloration. The outer layers bubble up, in this case it looks like the bubbled up layer was pounded back down.
