I found this site that details Nebraska gambling laws:

From this site, under the section that reads ‘28-1107 Possession of a gambling device; penalty; exemption.’, I found out that:
“ (3) Possession of a gambling device is a Class II misdemeanor.”

Then, I found this site which explains the penalties for a class II misdemeanor:

Under the Nebraska section, you will find this:

Criminal Code: 28-924 Official misconduct involves knowing violation of any statute or lawfully adopted rule or regulation relating to official duties

Class II misdemeanor
Max 6 mos.; $1,000

I’m not sure how current or accurate all of this info is, but it looks like the answer to your question is a maximum of 6 months jail time, and a maximum of $1,000 in fines.

Take care, and good luck.

One of my great aunts has owned a “coffee machine” in her home for as long as I can remember.

Slot machine ownership laws vary from state to state, in general, most of the states allow individual to own a slot machine if the slot machine meets one of the following three kinds,

Antique slot machines:
Slot machines that are at least 25 years old, provided that the seller explicitly states the age of the machine in the document. However, people in the following states may not own an antique slot machine due to laws prohibiting slot machine ownership in these states,

Alabama

Connecticut

Hawaii

Indiana

Nebraska

South Carolina

Tennessee
A few states require that slot machines be even older to qualify for antique status, but a few allow more recent machines. For example, in Idaho (Idaho Code 18-3810), an antique slot machine is a slot machine manufactured prior to 1950, the operation of which is exclusively mechanical in nature and is not aided in whole or in part by any electronic means.

It is recommended to check your local state laws regarding individual ownership of slot machines.

having to clean all the saliva and grease off of it.

I think the punishment is that you have to keep living there… I could be wrong.