Ciao Joseph, unfortunately your caseback is not unique. If it were special, then I also have one and we could corner the market with our two examples. There are two versions of the Mk II case (the 145.014 and 145.034). The xx.014 only came in steel and gold while the xxx.034 came in steel, plated and solid gold. The difference between the two cases is the sealing of the glass - there are two different types of gasket; different crown and (if I recall correctly), there is a slight difference on the tachy scale printed on the glass. Your watch is a very nice example but not unique, I'm afraid.
