Stamp on yo-yo says DELLS's BIG "D" BUTTERFLY. A Dell yo-yo from the early to mid 1960s. The packaging uses the word "yo-yo" on it, but the yo-yo itself does not. In the mid 1960s, this seemingly insignificant detail--among other things--played an important part in Dell eventually ceasing yo-yo production altogether to avoid legal action taken by Duncan over the use of their trademark "yo-yo". Originally retailed for $1.00; uses a metal axle with a starburst response.
This model was made out of tenite plastic and used a metal axle.
Compare with the Dell Super Star-No. 604. Why this Butterfly model and the Dell "Super Star" model--also a butterfly-shaped yo-yo--use the same style number on their respective packaging is unknown. One theory is that the name "Butterfly" originally came from Duncan Yo-Yos and was considered a trademark; Dell may have decided to drop the name "Butterfly" from their packaging and yo-yo and instead use "Super Star" to avoid litigation from Duncan.