That's a very nice bike.

531 frame, stays and fork mean it's a 700 series bike (the 531 badge on the seat tube will say something to the effect of 'guaranteed built with Reynolds 531 frame tubes and stays' and the fork decal shows it's 531). Looking at the distance from the rear tire to the seat tube- you can tell it's not a "racing" geometry bike- and looking at the decals you can tell it's an early 80s bike, and it does not have cantilever brakes- so that pretty much narrows it down to a 71X frame. That's a quality sport/touring frame and I think that build is spectacular. Not much I would change, if'n it were mine.