I’ve done that with canned salmon before — it’s a national brand, I forget the name, red label, and they didn’t used to put an expiry date on it, just a code number, and the reference table to get the date was on their website. Turned out it had been in my desk drawer for a long time, at work, and I needed to eat lunch. I think it was eight or nine years old, perfectly fine, just the flavor may have been less than it could have been. ;’)