Hi Warren, is there a name stamped on the top side of the square tubing that says Metallifacture? If not, it may be a jack made by Shelley. Shelley jacks had a sticker or decal placed on them, but a good chance a lot of them have been worn off. From what I can tell Shelly jacks were on early cars and a little longer in length, where as the Metallifacture jacks were shorter overall and a nub on the top side of the square tube to prevent the square tube being inserted too far, these jacks I believe are found in the trunks of later cars.
Brian