It should be marked on the barrel or chamber. If it is not, go to a gunsmith and ask for a chamber cast to be made.
Take the rifle to a gun shop so they can figure out what make, model and caliber rifle you have. There is no 84 caliber long rifle.
You will have to contact the company to find out.
Professional appraisal
Many do, but, not all the time. You will have to call to find out.
Basically impossible to do with just the serial number.
In the States, a 50 caliber rifle can be acquired after filing certain tax stamps. Once the tax stamps are paid and a background check has been cleared, then a 50 caliber rifle can be purchased at some specialty gun stores.
Gun shop, on line ammunition sales. Caliber is 6.5 Carcano.
Where can I find part for a Marlin model 57 rifle .22 mag
1863 was a civil war 58 caliber rifle. there is no history unless you fine the owner's family and the family knows details pertaining to the rifle.
You cant, unless you can identify the rifle correctly. Need to know ALL the markings, barrel length, caliber, etc.
You aren't supposed to dry fire .22 rifles because they are rimfire. If you want to do this, you need to find some .22 dummy rounds.
The Sears Model 42DL .22 caliber rifle was manufactured by Marlin Firearms, their Model 80. Check with Marlin for parts availability.