Fiscal and monetary crisis under Marcus Aurelius

[Epictetus]

I'm looking for information on the Empire's money woes under Marcus Aurelius. I've read the H.A. and Cassius Dio, but does anyone know of any other primary sources that mention this?

Also, Anthony Birley's biography makes a tantalising mention about debasing coinage. He lays the blame on the costs of the northern wars.

...debasement from 161-6; an improvement from 166-70; then debasement from 170-80.

Does anyone have an idea where I can find some information about the purity of coinage during this time frame? I'm wondering about the extent of the debasement and any sort of inflationary after-effects that could have cropped up.

Thanks!