With the demise of the A.C. Gilbert company, the Erector brand is now owned by their long-time British competitor, Meccano. It is still sold under the Erector name in the USA. Meccano actually introduced a similar construction set two years before A.C. Gilbert claims to have invented it in 1903. There are a handful of Erector Sets from the 1920s to the 1950s on display in the Miniature Engineering Craftsmanship Museum.
This is Erector Set No. 10053 “Rocket Launcher” (1959). It features a “50th Anniversary” sticker on the front of the original white metal box.