Any idea of the value of a winchester model 42 410 shotgun. I don't know the year. Excellent condition.

You will need to provide more information. Does it have a plain bbl or vent rib?, Is the forarm checkered or does it have rings (sometimes called a corn cob forarm), is the pistol grip plain or checkered? A plain jane M42 in excellent condition can be worth anywhere from $800-$1000.

Yep, whether field or skeet, and original or altered condition can make a world of difference. There's a strong market for the 42 in most any condition, but there's also a wide range of prices, depending on that condition.