How do I research for a price?

I have an old country store that we are closing down. I have an antique Toledo scale in great shape and a display case. I have looked in pricing guides but cannot find the scale or the case I have. I went on e-bay to try to find something like them, I didn't come close. People have come in wanting to buy them and of course they will try to buy for as little as possible. My old scale inspector told me there was only 1 ther scale older than it that was in use that he inspected and that it was worth some money but could not tell me any more because the job forbids it. He is no longer alive. Can anyone tell how to research to find out what it is worth?