Tom Waddington just alerted me that Google is now showing Google Guaranteed badges on Google Maps. You can see an example here for Simpson Air:
We’ve only been able to spot this label on businesses that are a part of the Google Guaranteed program with Local Services Ads. Google Screened listings do not have it (sorry lawyers). To get this label you would need to either be signed up for Local Services Ads or part of the very limited test of businesses that are allowed to upgrade their profile for $50/month.
Tom also noted that he’s not seeing this label on any garage door or locksmith listings.
Currently, we are only seeing the badge on desktop, not mobile. Also, you won’t see this in Google Search, just Google Maps. It’s possible that this is just a test so it might not be possible to replicate it on every listing participating in Local Services Ads.