These two series look the same to me:
|FRED CMDEBT (blue) and HSTCMDODNS (red)|
Maybe I'll forget to link to the FRED source page so you can't mouse-over the graph and see that the two sets of numbers actually differ a bit, and you can't click the Notes tab to learn that the numbers come from two different source tables.
Back before they changed things, FRED graphs were the best. There was no tweak that could raise questions. The data series were identified unambiguously, and -- given the top-border text and the vertical-axis text -- you could duplicate somebody else's FRED graph easily.
That's all gone, now. These days it's a shot in the dark.
// Find Part Two here.