Let's talk about dials first. Any double-signed Sea-Dweller is rare. The example above, retailed and signed by Tiffany & Co., is a very special watch. First, Sea-Dwellers were not exactly commercial products for Rolex – they were issued and assigned to men and women in special forces and technical pursuits. The idea of purchasing a mega-diver at Tiffany & Co. in New York City in the mid 1970s is strange, and that is why they are sought after. Also, the Sea-Dweller has more text on its dial than any other sports Rolex. There are seven lines on the Double-Red – add a Tiffany signature, and you're up to eight. That's a lot of text. And while it's not to everyone's liking, it sure is strange. And in this world, strange means collectible. There are supposedly some Cartier-signed Sea-Dwellers out there too, but I would be extremely careful about those. Though, really, I'd be careful with almost any double-signed watch unless from the original owner.