Currency. Paper money that has high acceptance internationally, like US Dollars or Euros, both can be easily traded by local currency pretty much anywhere in the world.
Idk how long the US dollar will have high acceptance internationally. I mean it may not change much or it may change a lot, depending on what happens the next few years.
My buddy grandpa left murica to go to his home country but traded all his dollars to local currency. When he got off the boat local currently collapsed hard. Huge fear of mine.
Russia is trying to make business with poorer countries to prop up the falling ruble, etc. I don't think the dollar or the euro has anything to be afraid of in the near future.
If you can't get a good stable currency or you have legitimate fears that the currency you can get is in danger of some kind of collapse, gold or silver coins would be your best second bet. In this case you'll want well known coins minted by an actual government such as an American gold eagle or the Canadian silver maple leaf rather than the coin shaped "rounds" that a lot of places sell. The rounds will have the same issue as jewelry, you'll have to haggle over weight and quality every time you sell one. Actual coins issued by a government mint will have pretty well established values so they will be easier to sell at a fair price.