What is Junkrat's secret treasure?

Hanzo has a unique conversation with Junkrat:

Hanzo: So, thief. Where do you keep your great treasure? Surely you don't have it on you! Junkrat: Treasure? S-sure, I don't know anything you're talking about.

And Junkrat has his own unique voice line on Temple of Anubis:

You think there's something worth stealing in that temple?

What's the secret treasure Junkrat is alluded to having by Hanzo? I know he and Roadhog are partners in crime, but has his treasure ever been revealed at all?

Solution 1:

According to his official story page, all that is revealed about this treasure is this,

He [Junkrat] came to notoriety when he discovered an extremely valuable secret in the bones of the omnium. Though few knew the nature of what he found, he was nonetheless pursued by bounty hunters, gangs, and opportunists wherever he went, until he made a deal with the Junker enforcer Roadhog, who grudgingly agreed to be his personal bodyguard in exchange for a fifty-fifty share of the spoils.

So, we are not told what it is (as of yet), only that it is extremely valuable.