I’m trying to figure out the difference between a 686 plus model# 13920 and model# 164194.

The 164194 is currently on the S&W website, but the 13920 isn’t there.

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?

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SWCA #3526

Interesting, if you do a search of “686 plus 13920” it shows up in at least 5-6 different sites. Maybe more.

S&W 686 Plus 357 Mag 4 in. Barrel 7 Rds Stainless. Model: LEDSW13920.

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.