Serial number or features or original receipt as a rule
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.
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.
If that is a US Patent, you can look it up on Google, and tell when the patent was issued, but it cannot date the gun- other than we know it would have been made AFTER the patent was issued.