However, in a possible indication of how seriously the SDR is being taken, the U.S. Postal Service is quoting SDR to dollar conversion rates:Convert the U.S. dollar amount to the special drawing right (SDR) value and enter it in the SDR value block. For example:INSURED VALUE
(Here is the original web page, without highlighting.).
A search of the U.S. Postal Office website shows that - as of April 2008 - the relevant web page did not have any reference to SDRs. The most recent revisions to this web page were made on July 30, 2010. However, I cannot tell whether the references to SDRs were added in the most recent July revision, or in a previous edit.
I am not implying that this is nefarious. I'm not entirely sure what this means, but - as far as I can tell - no other currencies other than SDRs and the U.S. dollar are mentioned in this section of the Postal Service website. At the least, it is interesting.
The Swedish postal service is also purportedly giving SDR conversions.
Update: Further digging shows that
some postal services have adopted SDRs as part of the international
multilateral agreements of the Universal Postal Union, an international organization of postal services. See this website from the Czech Republic, for example, from October 2009.
The earliest reference to postal service use of SDR's which I have found is a January 2007 version of the Swedish post office's website, stating:
responsbility for lost or damaged International Parcel Post is limited
to SDR 40 per mailing + SDR 4.50 per kilogram of the gross product
weight, in accordance with the acts of the Universal Postal Union (UPU).