I would start my search at Smith and Wesson first.
You take it to a gunmsith.
common Allen wrenches but to remove the barrel or barrel nut look for dan Wesson parts i recently bought nut removal tool as a kit,
In Smith and Wesson code, the 6 means the gun is primarily made of rust resistant stainless steel. The 37 designates the lightweight version of the model 36 .38 caliber revolver, and lightweight guns have aluminum frames. The -2 designation means that this revolver is the second version of this model. So 637-2 means a stainless barrel and cylinder on an aluminum frame based on a lightweight model 36 revolver in the second version (or first design revision) of this model which is designated model 637. The model 36 and model 37 Smith and Wesson revolver are 5 shot revolvers with a 2, 3, or (recently) a 5 inch target barrel. The 2 inch barrel is the most common version. The model 637 Smith and Wesson 5 shot .38 caliber revolver is only available in a 2 inch barrel.
Dan Wesson is now operated by CZ USA. Barrel nuts are available for about $15 plus shipping. See the link at the bottom of this page to link to the CZ parts page for Dan Wesson Revolvers:
It should be marked on the barrel.
4.5 or 6 inches
You will need to ask a gunsmith
Age of smith Wesson serial no 5K4166
What is the caliber, barrel length, finish, grip material, markings on barrel?
19.5 oz. with 1.875" barrel, 21.4 oz. with 3" barrel
Look on frame inside the cylinder area to find the model number of a Smith and Wesson 357 mag snub 2 in stainless barrel
It was Smith & Wesson Model 29 with 8 3/8" barrel.