Value of Encyclopedia Britannica?

I have 12 volumes of encyclopedias, (1862-1865?). On the side they say encyclopedia Britannica, ninth edition. The volume numbers are in Roman numerals, with American revisions at the bottom. All 12 volumes are burgundy with good writing.

Any idea what the value would be or where I could locate date. I have not been able to find a date, but am assuming by others I have seen on eBay that these volumes are from between 1862-1865.

Thanks.

By Jonathan D