[vegabook]

Like any liability of any entity, when you possess a swiss franc, you have a claim against the assets of the SNB. The assets of the SNB include a lot of gold and many foreign currencies. These assets have been accumulated in various ways, but are generally the foreign assets of the country in question (held on behalf of the people of the country by their central bank), plus the accumulated profits of the central bank over the years on this capital. Crucially however, just like "goodwill" in a company balance sheet (often a much larger ledger entry than any tangible assets), there is a large proportion of the value of the issuer's paper (be it equity or in this case, money) that is made up of intangible assets. Those intangibles essentially amount to the credibility of the entity, that is, the fact that other people believe that the piece of paper that it issues has value. Thus you have a claim against some of their assets, yes, but you're also hoping, just like with equity, that the value of the goodwill stays high (similarly for GOOG, AAPL or FB or any other company). The value of the goodwill is determined by the strategy and actions of the entity being seen as sound, and ultimately profitable, by the market.

Long story short, I don't personally know of any central banks who explicitly promise gold back against their liabilities anymore (this disappeared at Bretton Woods). Thus your claim is (mostly) on the credibility (goodwill) of the bank which is highly dependent on it not issuing too much paper.

As far as your claim on the tangible assets is concerned (the foreign currencies and gold), you will not be able to walk into the SNB with a 100CHF note and ask for the tangible share of what that represents. In practise, if the CHF loses value, the SNB will (amongst other measures such as raising interest rates and trying to put pressure on its government to spend less), protect your 100 CHF by selling its foreign currencies and gold into the market, "defending" your asset. That's how your claim on the tangibles works out in practise: the assets are paid back out to the market if there is pressure on the currency. Of course, again, only a small portion of the value of the CHF will be backed by gold and FX. The rest of the value comes from the fact that it is accepted by merchants and people in exchange for real goods and services. That's goodwill, otherwise known as "credibility" in monetary economics.