Ja-Do was a line of yo-yos produced by Duncan in the 1950's. The name Ja-Do is made as the first two letters taken from the names of Jack and Donald Duncan Jr. who ran the company during this period. Although an unpromoted line, the yo-yos were cheaper than comparative Duncan models and often sold better. To protect the Duncan brand, the line was therefore discontinued. As with all models from this era, the early Ja-Do models are sought-after collector's items, fetching high prices on sites like eBay.