Playskool produced these from 1983 to 1985. Mine has the original box (quite battered!) and the original key. Many of these on the used market have lost their key, although they do still work without it. The toy was popular with children and was featured in an animated miniseries in 1985 called Bigfoot and the Muscle Machines.
This is my Bigfoot Trailer. It's missing the tow hitch and a yellow cone but is otherwise in good shape:
This is the video of the animated miniseries that featured the Playskool Bigfoot.
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