Spare barrel assembly (includes loading lever, wedge screw but no wedge) for a Belgian made reproduction '1960 New Model Army'.
Read all about them here - https://www.1960nma.com/

Serial is C301, meaning this is for the Civilian Model series (and probably manufactured around 1960-1961) https://www.1960nma.com/second-model-civilian/

Still unsure? Check here https://www.1960nma.com/major-characteristics/

CONUS only, $130 shipped USPS Small Priority Box.