Ansley H Fox built some of the finest game guns made in America. Ansley Fox was an innovator, a consummate entrepreneur, and a perfectionist. He was more concerned about selling the best guns he could possibly construct, than he was about making a profit doing it. His graded guns are highly desirable to this day.
In addition to his firearms venture, he designed and built an automobile - which was also built to such high standards that it was impossible to make a profit.
The Sterlingworth model was introduced later in the company's evolution. It was intended to be a lower quality, more affordable model. As such, it holds less value than a graded Fox. However, the Sterlingworth model was also less durable than the more expensive graded pieces. Because of this, most specimens are in poor condition these days. Based solely on your photos, yours seems to be in good condition compared to most. The value of a Sterlingworth in Canada today will vary from $100 for one in poor condition to $1200 for one in excellent condition. IMO, yours looks to be worth between $600 and $900, depending on how tight the action is, on whether the bluing is as good as it looks in the photos, whether the barrels are pitted, etc.
Graded Fox guns are still made according to the original pattern by the Connecticut Shotgun Mfg. Co.