For various reasons I've recently been very interested in the theory of money and the question of the gold standard. It seems to me pretty undeniable that Marx has a commodity theory of money rather than just using the gold standard in his analysis because it was common at the time (As some seem to believe), otherwise his polemics against the Proudhonist schemes for expanding the credit supply by replacing specie with fiat currency would seem a bit incomprehensible, and it is pretty clear that Marx regards fiat currencies as a source of inflation. This also seems pretty well confirmed by the 20th century which so far has seen unprecedented (from the standpoint of 19th century capitalism) inflation at around the same point that specie currency was abandoned.
The problem I have is explaining why. Edgar Hardcastle, the SPGB economist who wrote a bit on the subject of Marx and inflation, seemed to regard it as basically a consequence of the ruling-class being overwhelmed by Keynesian ideology, as do most of the Austrian works on the subject (surprisingly, or perhaps not so suprisingly given that they were also pretty hostile to money cranks like Proudhon or Duhring, the latter even being mentioned by Mises in his notes on the history of the theory of money in the appendix to The Theory of Money and Credit, the Austrians seem to have some strong commonalities with Marx on the theory of money) which is not a very satisfying explanation.
One thing I did notice was that the abandonment of the gold standard by most of the major world powers coincides roughly with the 'epoch of imperialist decay'/'era of capitalist decadence', which gave me a vague thought that the abandondment of the gold standard might have been useful in facilitating economic imperialism. I'd be interested if any ICC'ers have any thoughts on this topic or can link me to anything that might help in drawing some kind of question. It seems that this is an obvious concrete example of a qualitative difference between 19th and 20th century capitalism which would go a good deal towards clarifying the concept of decadence.