Re: just wondering what this iver Johnson's worth?
Based on the shape of the stock and fore end your shot gun was made sometime between 1909 and 1925 give or take a year or two. I don't know of any accurate way to date these guns by serial number as, to the best of my knowledge, there are no records known to exist.
Depending on where you live, based on the pictures you provided, the gun should bring $150.00 and maybe more. If it were a smaller gauge it would be worth more.
Hope this helps.