"Nissan's Marriott code NIS is an automotive corporate code. Nissan's US HQ is in Franklin TN (Nashville area) with manufacturing in Smyrna TN and Canton MS. No FlyerTalk thread discusses NIS verification incidents. Automotive codes at Marriott are rated 'Low' enforcement overall — hotel staff in auto-manufacturing markets are familiar with major OEM codes but rates are modest enough that enforcement is rarely triggered. No specific NIS denial documented."

"FlyerTalk community specifically notes the MMM code as "the go-to code for the Minneapolis/St. Paul area, described as extremely reliable at local Courtyard and Residence Inn properties, with a low risk rating." One user documented using an IBM rate for 14 years at 80-100+ nights annually and "never once being asked for an ID." Another stayed 500+ nights and was never asked. The 3M code is regionally well-known near 3M's Minnesota HQ."

"Same- we stay at a very large Jw often just for a quick get away and have gotten to know a few of the staff. We’ve checked in numerous times and have been told there aren’t any upgrades - I’m Platinum. No worries, we’re just happy to be on vacation for a few days. Shortly after we’ve seen a specific front desk agent that is always friendly with us and she has upgraded us (yes, after we’ve checked in) at least three times…. And mentioned as she’s doing it, “idk why they didn’t upgrade you…. “ we never asked her since we were already checked in and we’re fine with the regular room. But certainly, a suite is a nice upgrade and very much enjoyed."