Yeah, I'm quite skeptical about SDRcoin too. But it might be somewhat good option if we add gold and silver into it. Is there an easy way to check the price of that basket historically?
If you mean just the SDR, there seems to be some 10 year charts available on XE.com
http://www.xe.com/currencycharts/?from=XDR&to=USD&view=10Y
http://www.xe.com/currencycharts/?from=XDR&to=XAU&view=10Y
Hmm... If we think what's the optimal way to analyze how stable a currency is, probably the best way would be to compare it to consumer price index? And not just one, but several from biggest economies around the world.
Then should be analyzed what combination of currencies, commodities, stocks, bonds, etc. can give most stable basket when it's compared to CPI-basket. We can't peg the new currency straigth to CPI because we need live feeds for feed producers. Or do we? Is it enough if we get only once a month a price for CPI?
Anyway, even if we just want to compare SDR+gold+silver-basket to USD, we need a tool that shows a historical price for that basket. It can be of course calculated from data of each asset but it will be quite time consuming to do manually.

Disclaimer: I don't know what I'm doing here, just thinking out loud.