Chaps, I'm looking at buying a Reverso and specifically one form the mid-late 90s. The Reverso Shadow Grande Taille. I have narrowed it down to the Shadow because I like the black/grey face and size (26mm x 42mm) but now I'm beginning to find watches advertised with different model numbers. It looks like some have a polished case and some a brushed steel case but can you experts give me the full details? What's the difference between say: 271.8.61 and 251.8.86 ?