Cast iron, if properly seasoned and cared for, is excellent for cooking and baking (cornbread, pineapple upside down cake, etc.) because trace iron is conveyed to the food. You can use an iron pot for frying, but it is unlikely that the benefits will be transfered through the hot oil into the fish. You can use any heavy, deep pot for frying. Make sure you have at least as much pot above the oil as below to allow for the addition of food and to keep spatters to a minimum.
It depends on what you want to do with the skillet. A deep cast iron pot is idea for deep frying, while a more shallow skillet is best for frying or baking.
what is the value of a martin cast iron skillet size 8 and 3'' deep
Cast iron skillets are used for frying and baking. I use mine to fry bacon and eggs, and to bake cornbread. They are non-sticking if they have been seasoned. To season a skillet, cover the inside of the skillet with a thin coat of oil and put it into a hot oven (400). Turn off the oven and let the oil cook onto the skillet. It will form a coating that is non-sticking. Never wash your skillet in soapy water because that will remove the coating. When the coating is washed off or wears off re-season it. I have a skillet that is over 50 years old. It doesn't wear out, it doesn't get dented, and if you always keep it seasoned it won't rust.
Deep frying
Deep frying and roasting
Deep frying
Depending on the exact dimensions, your cast iron skillet probably weighs in at 3 to 10 pounds, although it might seem like more. Even a cast iron dutch oven type weighs about 12 pounds.
The TFal 12 in Deep Skillet available at Walmart for $20 has the best reviews. While non-stick skillets are typically desired, cast iron skillets have a huge following and should be considered. If seasoned correctly, they will retain a slick surface similar to its non-stick counterparts.
Deep fat frying is a cooking method in which the food is immersed completely in very hot oil.
The food you are frying is covered in oil. It is also deep frying like you would for fish and chip's.
I find the wet based egg batter works well for deep frying and the dry flour and spices is best for light frying.
Deep frying adds a lot of unnecessary fats and oils where as roasting lets the fat melt away