2010 Standard Catalog of Firearms lists a Marlin 1887 Double Action Revolver. This is a standard top break style, last handgun made by Marlin and the only double action. Earlier guns were single action, and had a spur type trigger. Should be marked Patented Aug 9, 1887. They made about 15,000 of these from 1887 to 1899. Poor condition, $75, Fair, $200, Good, $500, Very Good $800.
Now, that is the BOOK value. The REAL value is what someone is willing to pay. An ardent Marlin collector would feel those prices are just fine. Other folks will ask if they can have some of what you're smoking, asking $500 for a top break .32.