Hi Brian, the lock was made by Detroit Brass Works, ca 1867-1890. Ira D. Bush is the patent holder and the pat. # is 63467. I’d guess the value range from $75 to $90. If it had been made and stamped for a railroad, I’ve seen those go for $85 to $150. I live in the Detroit area and love to collect local made locks, please p.m. me when you decide to let it go, I would enjoy adding it to my group. Bill