Jeff,
From the 30th Ed Blue Book: "HY-HUNTER INC. FIREARMS MANUFACTURING CO.
Previous trademark imported by Hy-Hunter Inc., located in Hollywood, CA.
Hy-Hunter Inc. imported single action revolvers in various calibers and O/U derringers manufactured in West Germany. Typically, prices are determined by their shooting value rather than their collector value. Prices generally range from $100-$175 depending on caliber and finish."
Made probably in the 1960s to early 70s. Röhm seems to be cited as the most likely manufacturer of their handguns. Doubt spare parts will be easy to find.
Also from the BB: "Röhm produced inexpensive revolvers for the U.S. marketplace during the late 1960s-1970s. Most of these guns were built as sub-contracts for U.S. companies and/or distributors (i.e., Hy-Score, a previous distributor located in Brooklyn, NY). Some of the models included are RG-7 through RG-88 (21 variations), Romo, Thalco, Valor, Vestpocket, Western Style, Zephyr, and others."