Too late to edit, but I've gone and done it: scanned through Sammet's Programming Languages: History and Fundamentals for languages with identifiable assignment statements. I skip assembly-style, English-like (COBOL etc.), and functional-style (LISP etc.) syntax, and for summary purposes ignore accompanying keywords like BASIC's LET.

Results:

ν = ε     18 (AMTRAN, BASIC, COLASL, CPS, FORTRAN, FORTRANSIT, JOSS, JOVIAL, Klerer-May, Laning & Zierler, MAD, MADCAP, MAP, MATH-MATIC, MIRFAC, PL/I, QUICKTRAN, UNICODE)

ν ← ε     4 (APL, DIALOG, IT, LISP2)

ε → ν     2 (MADCAP, NELIAC)

ν := ε     1 (ALGOL)

ε * ν     1 (BACIAC)

So pretty much everybody used ‘=’. ALGOL was an outlier, though admittedly more influential than BACIAC.