Serial numbers were not required before 1968. Check the barrel and receiver.
Yes, I have one in hand but don't know what year it was manufactured. With a six letter serial number.
50-100
Excel shotguns were made by Crescent, Crescent-Davis, Iver Johnson, and J. Stevens. If it was made by one of the first two, the number probably isn't a true serial number and the exact age cannot be determined. There are a couple of experts who MIGHT be able to place one of the other two into a range of +/- 5 years.
Probably.
Seldom exceeds 100 USD
http://www.scottcreative.net/Default.asp?ID=135
50-100 USD
There is no model 508 listed. A single barrel 410 Crescent Davis lists at: Exc V.G. Good Fair Poor 175 125 100 75 50
It was madein the1930s by J Stevens Arms Springfield Mass. ( Crescent was bought out by them in 1932) and the name changed to Crescent - Davis. Value can range from 100. to 500. depending on condition.
I was offered $5700 for mine
50-125 USD
0-150 USD depending on exact configuration, age, condition, accessories, etc..