If you can read french, here's a page about why 16 isn't used (anymore!) https://www.guichetdusavoir.org/viewtopic.php?t=36236 https://www.guichetdusavoir.org/v

If you can read french, here's a page about why 16 isn't used (anymore!) https://www.guichetdusavoir.org/viewtopic.php?t=36236 https://www.guichetdusavoir.org/viewtopic.php?t=36236 TL;DR Running out of numbers and putting in temporary measures requiring the 16 as prefix. Measures that likely didn't scale as well as expected since we moved on to a different system within basically 10 years.