This was a low quality pistol made by many different manufactures from the late 1880s to around 1915. The name 'Special Agent' was a tradename used by Fred Bifflar & Company of Chicago. They were mostly a mail order company and in direct competition with Sears and Montgomery Ward at the time. I believe they went out of business in the mid-1920s.

Many different companies contracted with them over the years to make low quality, inexpensive top break pistols in the S&W design. Two of the main ones were Crescent Fire Arms Co. and Meriden Arms Co. Iver Johnson also made some Special Agent models as well. Bifflar also stocked a close copy of the S&W top break under the name of Howard Arms Co., Chicago. It too had the name Special Agent on the left side of the barrel. This pistol was made by Crescent Fire Arms Co. as well as Meridian Arms Co.

I hope this answers some questions for you about these pistols.