You really need to give more information to get a good answer. If this is a double barrel shotgun, sn 272839 is what is called a Flues model invented by Emil Flues, introduced in 1908 and produced through 1926. It was offered in five gauges and 11 different grades and the value of the gun depends on the condition, grade, features, and, to a degree, the gauge. If you want a reasonable estimate of the value, have the gun appraised by a reputable gun smith or Ithaca collector.
You have a Ithaca Model 49 Saddle Gun which was mfg between 1962-1978.
double 12 ga
We can't tell from a serial number alone.
You have an Ithaca Miner model made in 1907 if it is a sxs double not stated in the ques.
You have an Ithaca Flues model made in 1920 if it is a sxs doubel not stated in your ques.
You have an Ithaca Miner model made in 1907 if it is a sxs double not stated in your ques
You have an Ithaca Baker model made in 1886 if it is a sxs double not stated in your ques
You have an Ithaca Flues model made in 1917 if it is a sxs double not stated in your ques
You have an Ithaca Flues model made in 1917 if it is a sxs double not stated in your ques
You have an Ithaca Flues model made in 1917 if it is a sxs double not stated in your ques
You have an Ithaca Flues model made in 1917 if it is a sxs double not stated in your ques.
You have an Ithaca NID model made in 1929 if it is a sxs double not stated in your ques