"Deutsche Bahn's Marriott code 11353 is a German railway operator code in the global GDS system. Outside Germany, this code is essentially unknown to hotel front desk staff. German Marriott properties near Deutsche Bahn offices may be more familiar, but the code is rarely discussed in English-language travel forums. No verification incidents found. European public transit company codes attract minimal scrutiny."

"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."

"I've never been asked, but last night I stayed at a SHS I had only stayed at once before and the clerk casually asked "what company are you with" and she was writing out my card. I suspect she was comparing to the rate plan I used for the reservation."