I happen to have one or two and I think they are worth $450-$650 depending on condition.
You have a winner! The .410 is a rather rare gun. Worth $5-$600 if in excellent shape.
As of January 13, 2012: 410 EUR = 339.398 GBP
Iver Johnson did not have a 410 gauge or bore in 1907. The 410 came along about 1920.
100-300 USD
The 410 hammerless essex shotgun is worth anywhere from $300 to $350 in good shape.
50-100 USD
800-2500 depending on condition
40-100
50 dollars
1942 Winchester lever action 410 is a common gun. For this reason, it does not have a lot of value and is worth between $175-$300.
Depending on condition, somewhere around $500. The .410 version is MUCH higher.