Whatever number of stamps end up in the file, my guess is that the thing to do is put at the start of the file a count of the number of bytes worth of stamp that appear, then put the stamp information itself at the end of the file. This minimizes the encroachment on the twenty remaining bytes of "reserved for future use" space; it also would allow us to have longish, easy-for-humans-to-read stamp information (either in addition to or instead of shorter, easy-for-computers-to-process information). My sense is that one stamp might be sufficient. A client picking up time zone information from multiple sources would use the one with the largest stamp. The stamp might be automatically generated as a function of the maximum "until" time appearing on a "Zone" line for the zone in question and the maximum "from" and "to" years appearing on a "Rule" line for the zone in question. Doing this would eliminate the need for separate maintenance of information from which to generate stamps; it would also avoid adding information to the zic input files that old versions of zic would not be able to handle. The down side would be that if we learned of a correction to zone information that only affected past times, we wouldn't get an *automatic* update of the stamp for the zone. Comments? --ado