Round rails & bearing fit?

Quick question here. I have the two used rails shown in the picture along with the four bearing blocks. No use for them so I thought I'd offer the pair for sale, but I noticed that the linear bearings have significant movement axially on their own. What i mean is, if I grab a single block I can rock it quite noticably length-wise ont he rail. If however I put a pair together they become nice and firm, there's no radial play that I can detect by hand. Is this normal or does it indicate significant wear?

Not sure about the bearings. There certainly shouldn't be radial play.
More interestingly, what motor is that as it seems to have an encoder?

It's a 3-phase stepper. It has no encoder, though it has the facility for one.