Yours was made in 1910
http://armscollectors.com/sn/winlookup.php

This was taken from another site...
1897 Winchester Slide Action Shotgun 16 Gauge 28"Plain Barrel,Exposed Hammer,Manufactured in 26",28",30" Barreled Versions. Take-down or Solid Versions,Plain Pistol Grip Stock.Manufactured Between 1897-1957 with Total Manufacture of over 1,000,000 Shotguns. (The 1897 is the Improved/Updated Version of the 1893 Winchester Shotgun)
Since the 1897 is embossed on the slide rail that marks your shotgun as being manufactured before 1912. It was also Winchesters first of the 2 3/4" Chamber guns Produced/Manufactured in history......

Below listed values are based on a percentage of Original Finish and Overall condition of the Firearm listed. Normal age and wear is considered in these reflected values.

90% Condition $525
80% " $455
70% " $355
60% " $300

Above listed values are current for October 2007, and are based on current market values on this firearm.

Please Note* With the sale of Winchester Repeating Arms Company, an automatic increase in value of all Winchester Firearms is anticipated and already being reflected in values. Despite the fact that your Shotgun has little of the Original finish, and it's value is reduced somewhat, this gun is still a highly prized Collectors item and will only increase in value. Do not attempt to refinish this Shotgun, as it will only negatively affect it's worth. If this is a family heirloom I would suggest you keep it and not sell it.