Try Blue Book of Gun Values
Check the receiver and barrels.
open gun where the barrels latchs,the model numbers will be right there.
It's a Belgian gun, the ELG is a Belgian proofmark.
Open the action. It is stamped on the water table, which is the flat part of the frame where the barrels sit. sales@countrygunsmith.net
Try the gunbroker.com, or do a google search on the specific barrel you need. Mid West Guns also carries Browning Barrels.
Try your library.
there are many avenues to find barrels for A5's. Try the "gunbroker.com" firearm barrel section. A5 barrels are sold there all the time.
You can try Hasting's. They make after market barrels.
To find out how many barrels are in a 500 barrel oil tank per inch, you would need to know the dimensions of the tank. Once you have the dimensions, you can calculate the volume of oil in the tank per inch and then divide that by the volume of a barrel to determine the number of barrels per inch.
More information is needed to give a specific answer. Barrels can contain anywhere from 31 gallons (beer), to 42 gallons (oil), and sometimes a 55 gallon drum is called a barrel. Once you know the size of barrel you're interested in, simply multiply the gallons by 19.2 by 100 for the answer.
Most old Damascus barrels cannot hold the pressures of modern smokeless loads. I doubt that you will find any black powder loads for that type of barrel. Hang it on the wall and admire it.
Information on this weapon can be found at any reputable gun dealer. And any bookstore will have catalogs on old or new firearms.