In spite of the name, there were several of these large oval "World's Largest Portable Roller Coaster" models manufactured in the early 1950s, and most appear to have retained the signage long after Miler made much larger portable wild mouse rides.
There were perhaps three of these large oval coasters built by Carl Miler: - One traveled with Royal American Shows. - A second was with Olson, sold to Don Franklin in 1957, and was offered for sale around 1959-1960. - A third may have traveled independently, but the details are not clear. West Coast Shows acquired one in 1961. This would have been the one at Playland.