Not sure about the model, but it's undoubtedly worth cleaning up and riding assuming there's nothing catastrophically wrong with it.

I'd agree that it's actually in pretty nice shape (to judge by the photos).

A Shimano 600 equipped bike (right down to the proper headset, not skimping on expense) by Miele would almost certainly have been built with a good quality steel tube set - perhaps Tange 2, Tange Infinity, possibly even some shade of Columbus, they used a wide variety in building.

If you search the forums a bit, you should be able to locate some Miele catalogs from the 80s, which might help with determining model name.

If it's your size, it should be quite excellent on the road...