Elgin Pocket Watch

If the SN given is from the works of the watch, the website below verifies you are correct in that this watch was made in 1899 which was the first year that this model was made.

http://elginwatches.org/cgi-bin/elgin_sn?sn=8403751&action=search

Average selling price in average condition historically on eBay is in the $75 range. As eBay is more of a wholesale value my estimate of value is in the range of $120 - $150.