What, if anything, does the patent date printed on a lock imply?

timof5stars

When we see a patent date printed on a lock (e.g. Sep 24, 1913), what does that tell us about the lock itself? Anything? Under one version I heard that it mean the lock itself had to be manufacture within 30 years of the patent date (in the example just cited, it would mean the lock was manufactured prior to Sep 24, 1943). I have seen others argue that no, this is not the case - that a patent date will be printed on the lock for as long as it is produced regardless of age. What say ye olde locksmyths?

wylk

I don’t think there is any requirement to remove a patent date after a certain amount of time has passed. Generally the only thing you can infer is that the item was made after (or on) the date the patent was granted.

Listing a patent adds a little prestige and warns competitors. After too many years it might become a liability, stating “look at us, we still make our old stuff and haven’t made any significant improvements.”

Whether to mark an item with a patent date or number is up to the maker. I think the only requirement is that it be a real patent, not something made up. And “Patent Applied For” (or Pat Pend, etc.) is legal only if a patent application has in fact been filed.

Are there any patent attorneys here?