In Henry J. Wehman’s The Mystery of Love, Courtship and Marriage Explained
(1890)
[https://archive.org/details/TheMysteryOfLoveCourtshipAndMarriageExplained/page/n33/mode/2up]
there are charts of secret messages Victorian flirters could send with fans,
parasols, gloves, and handkerchiefs.
Whether the handkerchief codes were ever in use (or mainly used
