The Gold Standard was a Central Bank Standard: In One Graph

Notice that even in 1913, more the 60 percent of the world's monetary gold was held by central banks. This is noteworthy because the Fed was yet to consolidate the monetary gold stock in the United States. Even while belligerent nations in Europe were lowering their reserves during World War I, the consolidation of the gold stock in the U.S. by the Federal Reserve pushed the proportion of central bank monetary gold holdings close to 80% of the world's stock. Only once the gold stock in the United States was mostly consolidated did the proportion drop. It is not unlikely that, even if belligerent nations had not abandoned the gold standard in 1914, central banks would have held 90% of the world's gold at the end of the 1920s. With this level of consolidation, even small increases in gold holding exhibit tremendous downward pressure on prices. The problem, then, was not that Europe was on a pseudo-gold standard, - gold exchange standard - after the war. The problem was that central banks employed only a single commodity and continually increased their demand for that commodity.