Update: Looked at this with Dmitry on IRC earlier and he confirmed that the latest version of the schema only corresponds to 2.1.134 (and later), and that the next-to-latest version corresponds to production releases as early as 2015-03-23. I have consolidated the table on Meta accordingly. He was also going to send the exact git revisions marking the introduction of each new schema version, but for now this might already be enough - I will leave this task open for a bit longer until we know that no more information is needed for the current analysis.

@Tbayer @Dbrant I was talking with somebody on the Android team a short while ago about the TOC and they mentioned that they thought the onboarding for the new TOC actually came a release or two after the new TOC. If so, the timing of this/table might be worth checking against the data. I see the impact of onboarding as secondary to understanding the impact of the floating TOC button, but might be worth eyeballing any bump to give a quick 'yay' or 'nay' on impact.

@JKatzWMF Good point. FWIW, I installed 2.0.105-releasesprod-2015-06-30 earlier today, which was the next to last release version before the button was added (per an earlier email by @Dbrant: "The new-style ToC button was released on Aug 11. (the actual version code of the app where this was first available was like "%2015-08-04%" and onward)")

I'm pretty positive I saw an onboarding for the old TOC when launching that version. But perhaps it was removed (instead of updated) temporarily when the new button was added? Confirmation for that from the developers would be great, or I'll try to check it myself later by installing 2.0.108-releasesprod-2015-08-04.