I just Googled "Singer 185 sewing machine" and then clicked on images. Looks to me as if it was designed to either be in a cabinet or sit in a "portable" base. They probably sold the machine both ways. One that has been taken out of a cabinet will not have the base part on it. You probably need to communicate with the seller to find out if the machine was originally a portable with a cover, or was taken out of a cabinet. HTH!
Edit: From looking at the pictures, the machine head can sit on a table without a base. However, then I think you may get the jiggling around that you are trying to avoid.