The key is to think in Metric.
one inch equals 25.4 millimeters
18.3 divided by 25.4 equals .720"
Twelve bore (12ga) true diameter equals .729", although it is often discussed as anything from .720" to .730"
Well the gun went 4 2 to 3 times what JABC should sell 4 [632 + shipping]....I E mailed the seller a couple days ago about any proof marks....This is what he said...under the barrels 822.. 843.. 18.5.. CJ or GJ.. and a crown over TJ......ring a bell for anyone???
The 18.3 stamp says 'this is a twelve bore gun' in metric.
Back in the 19th century the English didn't speak metric.
They don't do it much these days either.
The Belgians however did, and at the time that gun was built, the Belgians were the global powerhouse of gun production.
Given that whoever the guy was who answered the proof marks question almost positively *either didn't know squat about guns and proof marks, or knew that what he had was a european heap with London scratched on the rib* I'd trust the something over/under/beside/in juxtapose to a crown has about as much value as a used bandage.
So. What can we conclude?
We can conclude that the seller got a sum of money for something that was interesting enough to someone to pay that much for it.
End of story..?
We'll just see about that.
--Tinker