If the gun has a serial number and is from an American maker (or importer such as Browning), you can date a gun via a simple Google search, e.g. "Winchester serial numbers" or "Remington manufacture date". If the gun is European, it will have proof marks that may include a date (typical form "7/26" or "7 26" or similar). From time to time, there have been changes in the proofing laws in various European countries that will allow you to at least identify the general period of manufacture. This gets pretty complicated. You need to be able to discern among English, German / Ausrian, Belgian, French, Spanish, Dutch, Italian, etc. They all have had their own systems for over 100 years. If you contact a very knowledgable dealer of fine European arms, they may be able to help you out. You can google "German proof marks" or "proof marks", etc. to get started. Many, many "house brand" guns that were manufactured for sales through Sears, or Mongomery Wards, etc. are nearly impossible to date. Not all guns have serial numbers or proof marks, so then you need to find out when the gun was in production, and when specific markings or modifications came into production. Unless you have a collectible gun, it will be hard to find anyone with that kind of detailed knowledge.
You have to tell us who made it.
It is only an identifying mark. It MAY tell you what year it was made.
The gun was made in 1949.
No
If sn data has been published.
Serial number or features or original receipt as a rule
No way to tell. You can look up that patent, and it will tell you what year that patent was granted- but there is no way of telling when it was made, other than AFTER that patent was granted.
For SOME guns, yes. There are not records for all guns.
If you call S&W they will tell you when it left the factory.
Check old gun catalogs
You can tell by the model number and a few other details like the serial number of the air gun. But you will also need a Air gun catalogue, or contact the manufacture, or place the information here and let someone answer you.
Take your gun into a licensed Arms dealer. They will run the serial number on the gun (If their isn't one, this is illegal and you will be forced to forfit your gun to them) and they should run it and be able to tell you.