Municipal Bonds - prerefunded

[deaddog]

If any of you guys are big into municipal bonds, perhaps you can tell me where I can find a website that will quickly and easily tell me what the collateral is in the escrow underlying a given prerefunded muni bond?

In researching these, I've learned that the collateral can range from SLGS (the best, as solid as a standard T-bill, explicit full faith and credit of US) to something called Refco strips and other kinds of government bonds that are not explicitly backed by full faith and credit of US and are thus not as solid as SLGS.

But, when I search for bonds through my Vanguard account, I cant find any info on the composition of the collateral.

Any help on this question would be appreciated.

Thanks