While I am not a "wikipedia" fan, I'm sure that if you search Colt Thuer
on the webbernet you'll see some info on the very 1st attempt by Colts to circumvent the Rollin White Patent. The Rollin White Patent kept all manufacturers (except S&W) from being able to load the new-fangled cartridges from the rear.
Here are a couple more pics to help you understand a "front" loading cartridge conversion......
No need for a loading port as the cartridges are loaded through the cut out in the right front of the rammer lug, seated by the rammer, and ejected back out the same place. The ring turns to dislodge the spent cases (hence the E on the ring for eject) by firing the hammer on the spent rounds.
This is an original Colts made Thuer Navy cylinder (38 calibre), a reproduction ring, and an original second gen Colts 1851 Navy revolver.