State of Desolation
After the Fall, most of the survivors were put to sleep and taken care of. The government had to build new medical centers, now called Tombs, where people recovered. Depending on where they took you, you were designated a name and number tattoo on your left arm. The name groups were from Alpha to Zulu.
The further down the grouping you were, the longer it took for you to recover, but that also meant when you did you were that more resistant to radiation poisoning. The names have been a sign if you could survive traveling through radiation pockets, primarily for scavenging and treasure hunting. It’s common knowledge that those with Mike or later don’t have that much trouble surviving through the smog, so mercenary and scavenging outfits started checking applicants’ tattoos to gauge their usefulness, hence a mike-check.