If I remember correctly,they were made by Howa at one time. The ones I've seen look to be well built and shot pretty good. Hope this helps some.Maybe someone else will have better info. later. If it was made by Howa,they also produced the Weatherby vangaurd for a while.
I can't help you on what your gun is worth or by what company, but I traded a Remington 870 for one 2 weeks ago. Mine was made in Japan. It is chambered in 7mm Rem. Magnum. I plan on killing elk with it. YUM! It appears to be a really well built firearm.
Phideaux, the book lists several Howa 1500's in various configurations. Model 1500 Hunter, Model 1500 plus/ Lightning are two that are made in "various calibers." They all seem to range from about $300-400 in 98% condition. The 1500 Trophy (30.06) sells new for $528