Yep, really strange. Especially considering that the original helmet he owned is a "Hero" ROTJ and the only one we know.
I say "Hero" ROTJ because it seems to be a mix between the ROTJ mark1 reused ESB mark2 (ANH/ESB mic tips and ears, paper decals, square frown) and the mark2 (machined mic tips, ugly left ears, silkscreened decals, rounded frown).
Matt's original helmet (the one exposed at Comic Con by The Propstore of London) have machined mic tips, silkscreened decals and rounded frown...but strangely, ANH/ESB ears style and a faceplate which looks more to the ROTJ mk1 style than the "doggy" style of the ROTJ mk2.
I don't know if I'm really clear, but according to me, this helmet is unique (until we discover another one ^^).