If you've read Adam Tooze's The Wages of Destruction, you know a significant portion of the book is spent on Germany's foreign exchange crisis.
It basically goes like this, Germany in the mid 1930s has a trade deficit, significant debt obligations and is starting to be isolated by the world, so has trouble getting enough foreign currency to buy the imports needed to maintain its growing economy (and most importantly, its rearmament).
While I understand the basic mechanics however, one thing I do not understand is why they couldn't acquire more foreign currency through other means than exports, especially since the Reichsmark was nominally pegged to gold.
Is it because there was no centralized FOREX trading hub, because countries tightly controlled the export of their own currencies or because no one wanted to buy Reichsmarks? Was there not a market of speculators wanting to invest in various currencies?
I love Tooze, but this basic question plagues every re-reading of his magnum opus when I get to this section, so please enlighten me!
While the Germans pegged the Reichsmark to gold, they did not actually allow people to exchange Reichsmarks for gold, and never had even remotely enough gold to do so should they have allowed it. Even pegged to gold, the Reichsmark was essentially a fiat currency and the Germans found that no-one would accept it to clear trade deficits.
Amsterdam, London, New York and Bern had important foreign currency and gold training hubs, and it was common to deposit part of your national gold reserve in banks in one or several of those cities and simply transfer the ownership of that gold back and forth (but not move it physically) when they needed to clear debts.
Germany could use Reichsmarks to a limited extent, especially with nations they had a close trading relationship with and that usually bought their products, since those nations could use the Reichsmarks to buy German products. But unlike Dollars or Pounds, Reichsmarks could not be used outside Germany, so once you had bought everything you wanted or could from Germany, you had no ways to use the Reichsmarks.
So, even if you could exchange for other currencies and gold in the banking cities of the world, they would not accept Reichsmarks since you could not buy anything for them.
Thus the Germans were forced to "buy back" their own Reichsmarks with exports of raw materials (primarily coal), weapons, industrial products, gold and hard currency.
Other nations could often at least temporarily meet the need by taking loans in other currencies (primarily Dollars and Pounds), but the German state did not have that much trust after the inflation and defaulting on a lot of debt in the 20s and then the trade deficit, outrageous public spending on rearmament and nazi refusal to reverse any of these policies.
At the end of 1936, the German gold reserve was down to $26 707 000 (about 2/3 of the basket case Greece's) and despite attempts to make bilateral trade treaties with Balkan and South American countries, the German gold reserve kept decreasing and the German trade deficit climbed to 200 million Reichsmarks (about $80 000 000) per year by 1938. As you can see, the Germans did not have the money to pay for their imports, and if not taking the Austrian and Czechsolovak gold reserves in 1938 and 1939, the German imports would have crashed in 1938 and 1939.
So, while there were hubs to exchange and trade currency and gold, take loans and manage international credits and trade transfers, the Germans could not use the Reichsmark to trade, and had to use exports or gold to pay for their imports - and their trade deficits meant that they were quickly running out of gold.
The bottom line is that the world did not (rightly so, in my opinion) trust that the German state could meet its obligations due to its deficit spending and trade deficit and did not accept Reichsmarks as payments for hard currency and gold. This worsened the German situation, as they had to use their diminishing gold reserve to pay for their imports, which further decreased the trust that the German state would be able to meet its future obligations.