If you find locks, or triggers made by Davis, Chambers, L&R and a few others, most agree that you have a very good lock or trigger.
A "Siler" may or may not be a good lock. My reason for saying this is anyone can buy the Siler castings and proceed to put it together.
If it was done by a knowledgable person, it will produce a very good lock.
If it was done by someone who cannot follow instructions, or is a klutz with his tools, or his ability to heat treat steel correctly, it can make a disaster.
Barrels? Douglas, Getz, Colerain, Green Mountain and Rice all make very good barrels. There are some others who also make quality barrels but they are not commonly encountered.
These companies make very good products, but if your buying a gun which has been used, all bets are off.
Failing to properly clean or load and shoot the gun can screw up a fine product in less time than it takes me to write this.
Read some of the posts concerning buying used guns to gain a better understanding of what to look for by using the SEARCH button and "used guns" to find these posts.