According to info on Vintage Machinery, your grinder was built by the Paramount Division of Allegretti & Company, which was itself owned by Poulan, the chainsaw people. Paramount continued production of the Delco design for Sears.
http://vintagemachinery.org/craftsman/manufacturers.aspx
Your grinder, with Sears item number 9-1915, was offered in the 1981/82 Catalog of Power and Hand Tools.
https://archive.org/details/sears-tools-catalog-1981-82/page/30/mode/2up
It's hard to say what a "collector" will pay for most items, especially if the box is involved. You should check the "sold" listings of similar grinders on eBay to decide if it is worth your time and effort to find someone who will pay more than you did.
On the other hand, if you need a grinder and this one fits your needs, use it. If you don't abuse it and transform it into a "beater", it should last your lifetime.