Sessions came on the sean in 1903, formally E.N. Welsch. Your clock appears to be all original and they were offered in four movement types. time only, time and strike, time with calendar, time and strike with calendar. All were eight day clocks, yours was made from 1903 to 1915 best guess. Unfortunately clock values have fallen over the last several years,a direct reflection on our economy. Your clock is currently avaible from 150-300, a few years ago 200-375. The calendar clock is more valuable by 50-100. Clocks with advertising on the lower glass are more desireable. Prices will vary in different parts of the country.