Can anyone ID this badge for me?

[RelicCollector]

I recently found this in small bag of WWI and WWII badges and insignia. The back post is threaded, and the has a round knurled nut that screws on. Anyone out there know what this is, and how old it may be? Thank you.

[zwerge]

Hi,this COULD be just a commemorative badge sold on the occasion of a visit from a replica sailing ship such as the Swedish Goetheborg.

[SteveR]

It is an American Unit Insignia. They are worn on the lower lapel of the uniform coat for enlisted and on shoulder boards for Officers.
I do not know which unit this one represents.
Steve

[RelicCollector]

Thank you both for the information. I appreciate it.

[shadowwolf]

It looks like the ship 'the Mayflower', the pilgrim fathers ship.
Regards, Simon.

[Walkwolf]

It is an American Unit Insignia. They are worn on the lower lapel of the uniform coat for enlisted and on shoulder boards for Officers.
I do not know which unit this one represents.
Steve

SteveR is correct.
It is a WWII distinctive unit insignia, known as a 'DI'.