I’m trying to recall if any of the Locke bodied model L cars I have seen have a Locke tag. I may be wrong but I don’t think they do.
The under seat tag will give you the body type and the body types are all known and the builder of all body types is (pretty much) known. So if you look at your body type you will know who built it. Brunn, Judkins, LeBaron, Dietrich have body tags on the cowl bottom. Often on only one side. Locke..... I guess I just can’t remember seeing one.