Normally called earthenware but it is all pottery !! Earthenware is heavier and thicker than art pottery !! Your bowl looks like a factory made piece but I suspect it was sold as a second or imperfect piece !! It is not perfectly round as it should be and most all potteries will sell them as factory seconds !! There is no comprehensive list for pottery mfrs and there were many !! The initials on bottom are not the factory marks !! I suspect they are the decorators initials !! They would have been the ones to apply the drip and final glazing !! When you try to write on clay before it has been fired it will slightly carve into the clay !!Then the glaze is applied and made the initials darker than the clay it was made of !! Value,, yes but hard to say how much !! Some sell higher than others !! Check ebay sold prices for drip glazed pottery to get an idea of price !! If its a large bowl $30. to $50. is what I would expect it to sell for !! The foam flecks in the glaze are a selling point !!