Model 21’s will have plugged weep holes from the factory. Many LC’s have weep holes from the factory, I’ve owned 3, original field grades that did. I’ve also owned Ithaca NID’s that were drilled from the factory. Some Lefevers that were assembled by Ithaca are also found to have weep holes.
I’ve seen factory original LC’s with weep holes in different areas. Usually found right after the loop, some later LC’s might have had the weep hole in the reinforcing rib, and were plugged with a small screw. I have only seen guns with fluid steel barrels with these weep holes, I just haven’t had my hands on enough Damascus examples from each maker to have an opinion regarding those barrels.
I can only assume that the reason for the weep holes was that in a mass production process as most American guns were manufactured…the solder joints weren’t always 100% flawless, so when the barrels got boiled/steamed during whatever blacking process that company used, moisture was present between the ribs and these sets were drilled and oiled during the QC process. This would sort of explain why some are and some aren’t found with the weep holes.
Btw…..there are a few informative post from this forum over the years discussing weep holes found on various types and makes of guns, whether they are factory original or not, etc.