svn:needs-lock Files need lock, but I cannot find the property

I'm a little confused with something that is happening in our SVN. In my local checkout, some of the files seem to be set as "needs-lock" but I cannot find the corresponding property.

Most files in the checkout don't need a lock, only some
The files requiring a lock do not have a needs-lock property
There does not seem to be a needs-lock property on any of the containing directories
Both tortiseSVN and Eclipse (though Subclipse) recognise which files require a lock.

Can anyone suggest where the property/information is being stored for these files?

Solution

Posting this for the information of others:

After a lot of mucking around, it looks like setting a file to read-only (in windows) is enough for Tortise SVN and Eclipse to show the grey needs-lock icon (in Package Explorer or Navigator for Eclipse, Windows Explorer for Tortise SVN).

So it seems that the grey icon means that the file is under source control and the file is read-only, regardless of the 'needs-lock' property.