Antique Folding Horn Pen on sale Knife

Antique Folding Horn Pen Knife I would date this to the late 19th Century. It measures 13.5cm. x 24mm x 14mm. It weighs 138 grammes. It is 22 cm in length when open. It on sale locks firmly into place and is opened again by pushing down on the loop. There is minor damage to one os the scales. The knife would benefit from a minor clean.