That's a good question. There are actually several models. With the biggest difference being between the newer g2 and the older models. The pre 200,000 serial number models are not the easy open kind, in fact they can be a real…………….. Pain.
The easy open those with numbers above 200,000 have a center pivot point that is where the trigger attaches to the frame. The older, one pivots at the front of the frame. And there trigger/sear adjustment is inside the frame where under the barrel, you kind of have to take the barrel of to adjust, while the easy open models have their trigger/sear adjustment screw on the trigger itself. Both will give you a great trigger, with a little adjustment and spring replacement work. The G2 is well, something complete different, and since I have never, nor would I ever own one, I feel someone else should comment on them.
PS, the early models and the easy open, both can be fired without having to pull back the hammer, that is to say the gun won’t fire, but the trigger will, so you kind of have to open the action to cock the gun again, other wise the hammer won’t cock. This is great for testing one’s trigger, and such.
There are also differences in the hammers, some have a screw like head in the front, older models, what changes from center fire to rim fire and back again. One uses a screw driver to flip the screw changing which firing pin the hammer hits. The newer Contenders have the flip lever on the top back of the hammer.
You can get the older model up dated at TC, but you will have to tell them that you want the over travel screw added or they will send it back with the new hammer, and pivot point, but no over travel screw. I had to send mine back twice............................................................
Jim