I picked up this small adjustable at a garage sale not to long ago. I want to clean it up a bit. I want to remove the thumb wheel, but there is no screw. Any ideas would be helpful ! As you can in the picture, there is a small dot, where there screw should be.

Many adjustables just have a pin installed and then the hole is punched to keep it in place.  I have never removed one that wasn't already loose.  Does the adjuster spin freely or is it stuck? 
What make wrench is this and what size is it?  Looks interesting.

seems to me,most of the very old ones always have a screw,,did someone grind that down,as in grind away the screw slot

It is a Westcott made by Keystone MFG.Co in Buffalo NY. It's a 6 inch.  The thumb wheel moves freely.

Yep, okay, if the wheel spins freely I would leave it in place.  Disturbing it can only lessen the value of the wrench.  I clean most of my wrenches with a fine wire wheel on a bench grinder.  If needed I'll use a small wire brush to scrub in places the wire wheel can't reach.  It doesn't have to be perfectly rust free.  You will oil the mechanism and the oil will make the rust less noticeable.
There are chemical cleaners and conditioners but I don't use them so can't speak on how they work.  It's always possible that things are better left alone and maybe all the tool needs is some oil rubbed in.  Sometimes I use Boiled Linseed Oil rubbed in and wiped off.  I just cleaned a metal box for a socket set and rubbed BLO on it - it darkens the rust and highlights the paint color.

Exactly.

To the wire wheel we go ! Thanks guys !