it's not actually CLCan you link up the CL ad?
There has never been any Musicman with nitrocellulose laquer, and the bass in the pic looks just like a normal production bass.
I agree there haven't been EBMM basses in nitro - however I'm convinced my pre-EB sunburst 79/80 had a nitrocellulose finish based on the finish wear after only five/six years of use when I sold it (things we come to regret eh) - the sunburst had worn through on the slab top where the cutaway is on EB Rays, and in various other contact points. The shine also dulled down on it after a while....
Regarding the finish, it could be Graphite Pearl or Sapphire Black. Those can look matte under certain lightning conditions.