Look under Iver Johnson Arms and Cycle Company. Their hammerless revolver was sold under several trade names, including US Revolver Co. You can probably find one for sale on one of the online auction sites.
Unknown
Is it a real antique or a reproduction? It can make a difference. Yes
Oh my, YES! The Ruger .327 Magnum is a 7 shot, I have four .22 revolvers that are 9 shot- and there were antique revolvers-called Pepperboxes-with HUGE cylinders that held as many as 40 shots. (And my plain clothes weapon is FIVE shot .38 Special).
Yes
H2O
You can find antique pictures of that on the the wikipedia page or google images.
We cannmot post pictures here. Tranter, Adams, and Webley were British revolver makers in that time frame. Use a search engine such as Google, and select IMAGES from the tool bar, then one of the names and revolver- you should have several hundred images.
The answer to your question is -that will require an appraisal by someone familiar with antique European firearms, and will depend on model and condition. The Jongen Brothers revolver I have seen was an unusual "reverse break" type, hinged at the top, barrel swung up at the rear of cylinder. Have found mention of Jongen in 4 patents on revolvers, believe they were active in Liege Belgium in the mid 1800s.
Someone can see pictures of antique cars online on any image site such as Google images, or on websites that sell antique cars and post pictures to show the car to people before they buy it.
ask your local law enforcement agency
find an antique rifle dealer on your computer. ask the question and send pictures to show condition
You can find a 22 mag cylinder for a 22 mag revolver mod 21S MIW Germany on eBay. You may also be able to find one through antique sales and antique gun collectors.