Going through `/etc/mime.types` this afternoon, I discovered a delightful little gem:


The only reference to it I could find was a 1997 request for its MIME application. Of interest:

MIME subtype name : Vendor Tree - vnd.3M.Post-it-Notes  
Applications which use this media :  
Post-it Software Notes v1.5+  

Now that I think of it, my old man bought and used this with his Windows NT machines back in the day. They were rather cute.

Other information was decidely less helpful:

Required parameters : 3M Confidential

Optional parameters : 
3M Confidential

Encoding considerations : 
3M Confidential

Security considerations : 
Independent evaluation impossible due to specification non-disclosure.