The Essex trade name was made for Belknap Hardware of Louisville, KY, by Crescent until about 1932 and later by Stevens. If the barrel is less than 18 inches or the overall length of the gun is less than 26 inches, the BATF classifies it as a short-barrelled shotgun and possession is illegal unless it was properly registered in 1934 or during an amnesty period in 1968 and the registration papers are also in your possession along with a proper certificate of transfer to your name. The BATF isn't likely to prosecute if such a weapon was 'found in an attic', but if it should turn up while you are being investigated for some other matter, they will certainly include this violation with any other charges. If your model meets the minimum length requirements or is properly registered it should be worth $200 in Poor condition and up to $850 in Excellent condition.