I don't know how likely that is. I don't mean to imply that there is something inherently valuable in gold but rather that I think there is something inherently attractive about gold for humans, and I honestly don't think this is likely to change even with a, as you say, clean slate. Gold is pretty. Almost objectively so. And it's a rare enough commodity with a, I honestly believe, high enough demand (regardless of a clean slate) to make it incredible valuable.

Let's take your clean slate example and pretend that the lower economic class somehow prevailed. I would assume that under this outcome, the lower class, in order to limit or eliminate the power of the wealthy would engage in redistribution of said wealth. Initially it would be the common useful items that would be highly prized, tobacca and hummel (I'm assuming you mean barley). Throughout this time, I think gold would maintain its value, however the value of acquiring basic necessities would overshadow gold's value. As time went by and the economy began to stabilize, I think the value of these common items would drop in comparison and beautiful things such as gold and silver and diamond would become highly desirable again, and in vast quantities. Gold is pretty. We like pretty things even if they're not useful.

"Everything is worth what its purchaser will pay for it." ~Publilius Syrus

And humans will always pay hand over fist for gold.

Ultimately my evaluation of land being the most worthwhile asset is based on the requirement of survival and unless there is a massive cultural shift that destroys our love of gold (something thousands of years of time have failed to accomplish) then I still foresee gold being worth a lot. However in the immediate aftermath of a financial doomsday, land still seems to be the best commodity to not only stay on your feet, but perhaps to thrive. Once the immediate effects of the doomsday are over, a decade, a century (depends on the rate of recovery), gold will once again be worth a lot.

Honestly, I do think land is ultimately the best commodity to have under the circumstance of complete financial doomsday and indeed most financial circumstances. Ideally land that has a natural source of fresh water, underground or river. It allows you to be self sufficient, at least for your family, providing your own food and water. Perhaps if you're prepared enough you can set up some solar panels to generate a small amount of electricity for yourself, although I'm nowhere near knowledgeable enough on this subject.

Obviously squatters are an issue but if you have excess land than what you and your family needs to live and grow food then you could very well rent out your land, obviously not for money, but some other service, helping out with the farm, defence of land. A feudal agreement of sorts.

Of course if no one respects your property, and are willing to kill you for it, then no commodity is better than any other. Even guns, you're just one person.