Gorgeous! Love that wood.
I'll guess that it was made in the late 1870's or very early 1880's. No hammer blocking safety's so probably rebounding locks. Percussion fences and hammers. Wedge forend fastener.
I have a Snider in 577 and have done some loading for it. I'll just say they can be a bit difficult to get to shoot as the bore and groove diameters were generous. Here's hoping that your rifle shoots as good as it looks.
The Lee dies may or may not work for you. If you haven't loaded cast bullets before or haven't loaded for a double rifle a little research may be in order. You will need to reasonably match the bullet weight, diameter and velocity to the original load in order to get it to shoot together. Be sure to slug the bores to get an idea of the bullet diameter you will need.
This site may prove helpful.
http://www.castboolits.gunloads.com/
Hope I'm not "preaching to the choir", please forgive me if I am.