On Tue, 29 Nov 2011, Jon Hylands wrote:

> If you pull a virgin 4.2 All-in-one image off squeak.org, you'll see that
> that method does not exist anywhere in the image, so it obviously came from
> some other package...

It was introduced in Squeak 4.3, see 
http://lists.squeakfoundation.org/pipermail/squeak-dev/2011-March/157820.html