What fraction of Leonhard Euler's output actually came after he went blind? Two Tier-2 sources conflict ('half of his output' vs '≈a third in the first seven years')

claim-euler-produced-large-share-of-output-after-going-blind rests on a quantitative claim (sourcing floor Tier 1–2) for which two Tier-2 sources give figures that do not match:

• Allyn Jackson, Notices of the AMS (2002): "half of his output came after his blindness" (of ~850 total works).
• Mele & Sicignano (2021), via Calinger's Leonhard Euler: Mathematical Genius in the Enlightenment (Princeton UP, 2019): "almost a third of his results in the first seven years after completely losing his sight at the age of sixty."

Why it matters. The Euler case is the "memory / dictation" leg of the blind-mathematician pattern (claim-blind-mathematicians-independently-reinvented-private-notation). A clean "half" is quotable and memorable — exactly the kind of statistic secondary sources round — so the note should not go past seedling until the number is grounded in a primary catalogue rather than two disagreeing retellings.

What would answer it:

1. A primary bibliographic count. Euler's Opera Omnia and the Eneström index (E-numbers) catalogue his works with dates; the fraction produced after complete sight loss (~1766, age ~59–60) can be computed directly rather than quoted.
2. Calinger (2019) directly. Mele & Sicignano cite Calinger for the "almost a third in seven years" figure; reading Calinger would confirm both the figure and the window, and clarify whether "half over the full remaining period" and "a third in the first seven years" are compatible.
3. Resolve the dating discrepancy noted on the claim-note: the age at total blindness (the sourced figure is "at the age of sixty," vs "around 27" in the older anchor note, which likely refers to one-eye loss).

Candidate next move. Search for the Eneström catalogue / MacTutor's Euler chronology online, and check whether Princeton UP or a review of Calinger reproduces the post-1766 count.

Progress, 2026-08-01 (still open — not answered). A follow-up search did not locate the Eneström-catalogue count, MacTutor chronology cross-tabulation, or Calinger primary text named above, so the core fraction is still [unverified — could not confirm or deny after search]. It did surface three findings that sharpen the conflict without resolving it: claim-euler-half-output-figure-traces-to-1883-rudio-lecture (the "half" figure traces to an 1883 Rudio lecture with no independent bibliographic count behind any of its three known appearances); claim-eulers-total-work-count-unsettled-across-sources (the denominator itself ranges 560–866 depending on source); and claim-euler-seven-years-figures-describe-different-windows (the "seven years" in different accounts of Euler's late output are not the same seven years). What would still answer this: the same three items above, unchanged — a direct walk of the Eneström index/Euler Archive listing, or reading Calinger (2019) directly.