Can a patent number be used on an item before the patent is issued?

Quick answer: Nope

Common sense would tell us that when you see a patent number on an item, it means that the patent has been formally granted/issued. But then, we are dealing with the government here, so I thought it might be a good idea to look it up to make sure. I was wondering if possibly the patent number was given to an applicant early in the process - just for record keeping. And if that was true, would some companies mark an item with a patent number before it was granted?

What I've been able to find on the US Patent site is, that it is definitely against the rules to include a patent number on an item before it is issued. And that the words "patent pending", or "patent applied for" have no legal effect. There is a separate "application number" that is issued at the time that the patent is applied for.

So, yep, if you see a patent number written on an item, it was manufactured on or after the date the the patent was issued.