A Cheerio store display sign advertising that the store was Cheerio headquarters for contest supplies. Those contest supplies would have included Cheerio-branded yo-yos, yo-yo string packs, and trick books.
The sign was likely displayed in a store front window or somewhere inside the store near the Cheerio yo-yo display. Dating the sign is tricky. If you base the year on the string pack seen on the sign, it may be placed about mid 1950s through mid 1960s.
The yo-yo to the right of Contest Supplies is an unknown Canadian model or just an illustration design and not any particular model. The text on the yo-yo's label says, from top to bottom, left to right:
"TESTED & APPROVED FOR ALL TRICKS
THE KIND THE CHAMPIONS USE
MADE IN CANADA TRADE MARK REG.
FOR 2 HANDED PLAYERS"