I have recently came into a Lefever sxs 20ga. shotgun that looks old.Its has Levfever Nitro special on the right barrel top and Lefever Ithica new york on the left top.It is a box lock and has a flying duck on each side.Can some one tell me what years these were made?It looks like it was made in the 40s or 50s at least.Very nice little sxs and was love at first sight when i found it.would the value be around 5-600 dollars?Any info would be very appreciated.Thanks in advance.