Where can you find any information about a Newport 20 gauge shotgun with the markings E 303 HX on the trigger plate?

'Newport' was a trade name used by the HD Folsom Arms Co on shotguns they sold to HSB & Co, a hardware/catalog store giant in Chicago. These will be from about 1890 or so until possibly the 1920's. I am betting it is a single-shot shotgun, and if so could have been manufactured by Crescent, Hopkins & Allen, Stevens, H&R, or a number of other manufacturers that dealt with HD Folsom. We'd have to see the receiver to be sure. The markings on the trigger plate may function as a serial number, but are of no significance. sales@countrygunsmith.net