I am the very happy new owner of a 1937 Gretsch tenor guitar.
Now that the instrument is in my possession, I thought I would add it to 'The Gretsch Pages' instrument database, both as a record of my ownership, and to help expand the instrument database of that site. You can see the registry entry for my tenor guitar here.
During the registration process, I was asked whether or not I wanted to keep the serial number of the instrument confidential. I chose not to, thinking that having the serial number posted in the entry would be a form of certification that I owned that instrument. (Clearly, I know this wouldn't be legal proof of ownership, but it does seem like a nice public confirmation that the instrument is mine).
Anyways, I'm wondering why anyone would not want the serial number of an instrument they own made public. I can't think of a downside. Thanks.