The cornucopia is the emblem for the Steward in some lodges.
It also features in (some) Knight Templar rites (on the mitre) and in the “Past Masters Degree”.
Is that thing on the top left of this German 3rd degree tracing board below also a horn (of plenty)? I don’t know a 3rd degree connection to the horn, so maybe it is something else.
A nice variety is shown here on a sixth degree (Chevaliere de la Lune) Adoption tracing board (held by the woman on the globe).
Top: Duncan’s Masonic Ritual and Monitor (1866) by Malcolm C. Duncan
Middle: Feddersen (Die Arbeitstafel in der Freimaurerei Band I (1982) D/41, P. 375), Feddersen only says that the design has a French source.
Bottom: untitled and undated document in the Bibliotheque Nationale de France FM4 (1323), digitally available