why are you interested in this regulator in the first place? Is Mares a brand that you are wanting to purchase for a specific reason, or have you found a very good deal on this?
They are very old, but should still be able to be serviced. It is a V16 first stage as shown in the picture, and the second stage is an Akros. Mares, unsurprisingly since they're Italian, like to fiddle with things and tend to remake their regs quite regularly as opposed to companies like Scubapro, Poseidon, Aqualung, Apeks, Atomic, etc that get a good design and stick with it. Mares feels the need to come out with something "new" every year or two. It is what it is. Call a service tech and verify whether they can get parts for these regs, but it shouldn't be a problem.
The history of this regulator is as simple as Mares trying to capitalize on the Titanium craze in the early 2000's, nothing more. Titanium is not a justified material to use in scuba unless you really need to shave ounces out of your luggage for travel, it offers no benefit in performance over brass, but has limitations in terms of O2 mixes. It is a good enough regulator, but I would look at other brands if I were purchasing.