Blue Book of Gun Values, old gun catalogs
Unknown.
The caliber of a Philadelphia derringer with Jukar 054167 Jukar stamped on the barrel is not known. There isn't enough information to determine what the caliber would be. A gun collector would be a good person to ask.
I have one and it is a 7x57 caliber is stamped on the left side of the barrel.
The caliber of the firearm should be stamped on the barrel.
caliber and maker's name
Usually caliber and/or serial numbers.
Well, it depends on what you mean. The caliber is "determined" at time of production based on whatever caliber the manufacturer wants it to be. The caliber can be determined later by looking on the barrel. The caliber will almost always be stamped somewhere on the barrel.
The Stevens will accept whatever caliber designation is stamped on the side of the barrel.
On the top of the barrel near the flash suppressor it should be stamped with the caliber and rate of rifling. Example - 5.56 Nato 1/7.
If it is not stamped on the barrel or you do not trust the barrel markings, the only reliable way is to have a gunsmith make a casting of the chamber.
No. Only use what is stamped on the barrel.
Should be marked on the barrel. It is impossible to tell caliber from the information you provided.