I am sorry for your loss. The value of a old machine tool depends on a great many factors. Some of which are:
1. Location. Where you are in the upper mid west I would expect prices are lower than in the south or west as due to your surroundings previously being a manufacturing hub, the supply of old machines is higher.
2. Condition. Most 70 year old machines have a lot of wear on them but some were lightly used so are worth a lot more. The machine may just look to you like a greasy mess but could be a gem. It could also be worn out junk. You would need someone knowledgeable to inspect it to assess condition.
3. Tooling. There are lots of extra add on items that can be very valuable by themself. Often an owner of a lathe may have more money invested in tooling than they spent to buy the lathe. A lathe typically comes with a handful of these items. Additional fixtures and tooling can be sold separately to get more money. Someone knowledgeable but uninterested in purchasing needs to look over what you have. Then you need to decide how much time you are interested in investing to get max value as it is a lot of work to sell say 30-50 individual tools. Even using Ebay you have to price and list everything and then pack and ship it. Maybe it is better for you to sell everything to one buyer even though you will get less that way.
4. Time. If you want it gone right away you may need to take less. If you are in no hurry you can start a little high and come down a little every month until it is sold. Are you willing to have multiple men you don't know come to your house to look at it? There are companies that buy and sell lathes but of course the pay wholesale prices which are half of full market value as they have to move it, store it, advertise to find a buyer, and make a profit.
Ideally you find someone local who is trustworthy and knowledgeable who can come look at what you have and give advice on the local market for a lathe as a hobby lathe is too costly to ship.These things are usually sold to someone within less than a 2 hour drive.