Dufour have always fitted DZR fittings as far as I am aware. Valves being nickel plated is not unusual, and does not worry me along as they are DZR. Normally DZR valves have ‘DZR’ embossed on the body.
Did you buy the boat from new? If so, I suggest you speak to the Dealer.
If you did not, buy from new, then have they been changed by a previous owner?
I have heard reports of yachts, not Dufours, getting through DZR hull fittings in a matter of a few years if moored in an area with a lot of stray currents – (i.e. in a marina) This was a particular problem in my marina, where a live cable was left dangiing in the marina. – luckily the other end of the marina to where I am moored so I wasn’t affected.
I replaced my heads hull fittings last year, (see Dufour News No 122). They were 22 years old and were fine – i needn’t have bothered to change them.