One used Master Lock #34 trailer hitch coupler lock. This is the preferred original design painted copper, not the new design that is painted black.
It comes with two keys. You will need to get an Allen wrench - the key opens up a hole for the Allen wrench to snug down the lock over the trailer hitch coupler.
It fits 2" Atwood and 2" Fulton trailer hitch couplers and probably some others.
The lock works as it should. It is constructed of material that won't rust.
$25 cash
To the guy in Minnesota - I did respond to your e-mail. Check your spam filter.