Whitney purchased the 1866 patent from Laidley and Emery in 1870, and put it into production the next year. But the mechanism was complicated, and expensive to produce, so Remington outsold Whitney. The design allows the Whitney's 3 piece hammer to let the shooter put the hammer in half cock, and open the breech block to load. So unlike the Remington that goes to full cock, the Whitney doesn't need to lower the hammer after loading, and can't drop the hammer by accident when closing the block.
This one is in .45-70 and has an excellent bore. The .45-70 in these guns didn't get offered until around 1874, so mid production, or later. It has a carbine style ladder sight, and a sporting graduated tang sight also. One of my favorite Rolling Block rifles.
As for reassembly....it ended up taking me 5 or 6 tries to get it assembled, and actually functional! I thought after taking it apart reassembly would be no problem. I found it locked up each time, until I finally realized the dual springs stacked on the lower tang for the hammer and cam need to be the last thing to install. After that it was back to working great again.
