Searching for files that do not have a file extension

I have a 2Tbyte external backup drive that has some files on it I'd like to find. Is it possible to search for files that do not have a file extension, if so, how?

If I use wildcards and use a single * rather than . this finds ALL files on the disc even those with an extension.

The wildcard you want is:

~(.)

Follow-up:

~(.) may only work in some places (e.g. the filter bar), but this more explicit version should work everywhere (e.g. the find panel's Simple mode):

~(.)

That's got it ~(.) works a treat. I take it the tilde means NOT?

Yep: Pattern Matching Syntax

Cheers, thanks for the help, much appreciated.