There are no five digit product codes for the 686 or 686 plus listed in the latest Standard Catalog of Smith & Wesson. All the product codes I’ve ever seen are six digits long. Are you sure of your number?
I don't find a lot of information "elsewhere" to be particularly accurate.
Not saying this is the only site for reliable information, but I've found in my 10+ years as a member here that this site is the most consistently accurate for all things S&W.
That said, are both of the codes you have printed on box labels? I'm wondering if one of those might be a limited-edition or a run made for a distributor. I'm also not familiar with 5-digit product codes.
Thanks, I still don’t know what the difference is (if any) but I just found the “13920” on the S&W website under their “Guardian” sales program. Which probably checks with the “LE” prefix I saw.