Muley,
I looked at the radiographs (x-rays) in Neal/Jinks and I can't see anything wrong. All the pics were of the other side and with the hammer at rest, though. All I can think is that either there is no upward spring tension left on the trigger return spring (the flat sping in front of the mainspring), or there may be a burr or something keeping the trigger return lever from camming the trigger back. I would carefully remove the return lever and inspect the pin it rides on, and the frame under it.
The way I do that: use a small pair of needle-nose vice grips with pieces of rubber hose or several layers of thick tape sleeved over the jaws. Compress the return spring just enough to take the tension off the lever, then lift the lever out. You can then take the plyers off and see if the spring has enough upward tension. If everything checks out ok, and you still can't figure it out, email me and I'll take the sideplate off one of my 1899s and take some pics for you. They use the same mechanics. I had a 1902, but I sold it last year. I successfully took it apart and put it back together, so there isn't much to it.
Good luck,
Chris Taylor