Without proof marks, I would think the gun predates 1892. It was most likely meant for blackpowder loads and you would need to keep the pressure lower than CIP standards. Would the gun be strong enough to handle CIP - quite likely. But that was not the makers intention and his design limitations should be respected. You can easily reload within the blackpowder limits.

Nice gun. It would be interesting to see the markings on the underside of the barrel flats and just ahead of the flats.