Some files keep their history in their opening characters, and the GIF is a small masterclass in the practice. Read one by its first bytes and you will find not only that it is a GIF but which GIF it is, because the version rides inside the signature itself. There are two to find. The earlier reads 87a; the later reads 89a. The difference of a single digit at the very front of the file marks two moments in the format's life.

87a came first, the original specification, capable and widely used. Then came 89a, and with it an addition that changed how the format would be remembered. The later version introduced the extension that made looping animation possible, the mechanism behind every short, endlessly repeating clip the format is now famous for. That capacity is precisely why the distinction is worth marking. A file that only ever declared itself a GIF would leave you guessing what it could do. A file that declares 87a or 89a tells you at once whether it belongs to the era before animation or the era after.

This is the exhibit's point about signatures in miniature. The signature is not merely a label saying what kind of thing you hold; it can also record which generation of that thing it is, folding a version number into the identifying mark so that reading the first bytes reads the file's lineage as well. The sniffer shows this directly, examining a file locally and reporting back not just GIF but the exact variant, 87a or 89a, sitting at its head. It is a neat demonstration of how much a few characters can carry. The people who wrote the format could have kept the version somewhere deeper, buried in the structure, but they put it up front where anyone reading the beginning would find it. Because they did, the signature answers two questions in one glance: what this file is, and when in the format's story it was born.