⭐ Merited by Findingnemo (1)
If you have generated a seed phrase or private key, the wallet you used can give you the option to backup the seed phrase or private key using QR code. You can use the QR code as backup. So that anytime you want to recover the wallet you can use the QR code backup to recover your wallet as it contains the seed phrase or the private key. But I will not advice you to use this method for backup. It is better you write down your seed phrase instead which is better and seem more secure in my opinion.
You can always restore a simply written seed phrase (on paper, metal or any other way) without third-party applications. In the case of QR-code backups, you will need some kind of application that converts from one format to another. This moment is the most unsafe. Why create an extra (dangerous) intermediary between you and cryptocurrencies?Any thought on how to transfer Compact SeedQR to the steel plate? I'm asking because master SEED can be presented now in both SeedQR forms on the screen of Passport 2 which is device to manage my bitcoin stash. I thought about mapping the transparent film with the relevant image and use it for the further transfer to the metal plate. But maybe you have a better view on this matter.
This brought up another thought. Transfer the bitcoin address into QR code format and apply it (laser engraving) to a small metal plate (like an army badge or medallion) and show it to receive payment or donations. Fast (QR code is always on your neck / pocket), convenient (takes up little space) and cool. 
Well, or wear it as a keychain.