I still remember burning the dsl livecd image to a mini-cd shaped like a credit card (edges trimmed off) and using it on university workstations.
Yeah, I had one of these in my wallet with DSL.
I'm sure I burned a Gentoo stage 1 boot ISO onto one of those card-sized discs.
These days, DSL is just Debian with less installed. The 700 MB is a curated list of software chosen to fit on a CD image but you access to the full Debian repos.
Current version clocks in ~700MB, again very small when compared to any modern Linux installation media.
On the other hand, it seems like DSL takes a more extreme approach to slimming down i3/XFCE route, plus DSL contains Dillo which is arguably the latest modern-ish (to the most extent possible) and lightest browser in existence.