[philipkglass]

Cobalt has only one naturally occurring isotope, so I don't think you can use any tricks from chemistry or physics to track it back to the source after it has been separated from ore. Instead you need tamper-resistant supply chain documentation all the way back to the actual mine.

[dv_dt]

I'm not familiar w/ cobalt, but materials are rarely 100% pure. One might look at non-cobalt materials associated with the pure material and what ratios they're in? Again not perfect but something.

[solidasparagus]

I think one of the problems is that the cobalt doesn't reach component manufacturers until it's been through a series of smelters/refiners.