"BlackRock's six-digit numeric code (340965) is notably less circulated in public forums than three-letter ticker codes, slightly reducing discovery risk. However, finance-sector codes in NYC and SF see elevated scrutiny. "Medium-risk codes are subject to spot checks, especially during mid-week peak business travel, with properties in major metropolitan areas being the most likely to ask for a badge." BlackRock's NYC concentration and premium rate level keep this firmly at Medium. Numeric codes also trigger less "code sharing" behavior, reducing overall exposure volume."

"I have been asked to show some proof couple of times. I normally show my corp id but credit card with employers name on it has worked, too. As would probably just showing my laptop with employer e-mail account or whatever. My impression has been they are happy with just about anything that proves I'm working for the company whose rate I use and why wouldn't they."

"I don't do mobile check-in if I'm wanting to upgrade. I check the app before I go in to see if any suites are available to book during the duration of my stay. If there is I just say "Would it be possible to get upgraded to an available suite with my platinum benefit?". Of course this is typically at the hotel that I stay in about once a month for 3 day at a time for work. The front desk pretty much knows me and know that I am fairly low maintenance."