In several episodes Mr. Wilson (George) says I'm going to
"work on my coin collection".

How do you "work" on a coin collection ?

There are several ways:

* sort coins and put them in order by date and mint mark
* make lists of coins needed to complete sets or series
* go through dealer catalogs (or online listings today) to buy or bid on coins
* inspect coins to determine each coin's condition
* look up the values of the coins based on scarcity, condition, & precious metals
* insert coins in folders or holders
* write labels as needed

Cleaning is another option, though usually frowned upon by serious collectors.

Wilson had so many interests.

Coin collecting
Painting
Bowling pro
Collecting stamps
Bird watching
Flower gardening and photography
Neighborhood Beautification committee
Sells houses
Clever enough to build a barbecue
Seems very mathematical and worked temporarily at a bank
He seems to be on many committees and in one episode got an award from the Community Chest.
His former employer wants him to come back to work.
Anything else?

Playing chess with someone in another location.
In the same lodge as Mr. Finch the druggist.
Golfing in the rain.
Thinking of ways to avoid going to the dentist

Wilson had so many interests.

Coin collecting
Painting
Bowling pro
Collecting stamps
Bird watching
Flower gardening and photography
Neighborhood Beautification committee
Sells houses
Clever enough to build a barbecue
Seems very mathematical and worked temporarily at a bank
He seems to be on many committees and in one episode got an award from the Community Chest.
His former employer wants him to come back to work.
Anything else?

Wow, no wonder Dennis loved him so.