"GM's Marriott code GMC is confirmed in FlyerTalk's publicly usable codes list alongside Ford (FRD) and Toyota (TOY). No specific verification-denial threads were found. General Motors has major hubs in Detroit/Metro Michigan, and Marriott properties near the Renaissance Center likely handle many genuine GM employees. US verification is rare — geography matters most, with hotels within 5 miles of GM's corporate HQ being the exception."

"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 have never been asked and I have 51 nights in a Marriott this year using our corp rate."