Oliver:
As I think you and I discussed, I bought the bass from the original owner, who was very knowledgeable about it and a good guy, besides. I recall that he told me that the bass was originally built as either the first or one of the first basses that had the noise upgrade, so perhaps the upgrade happened before Alembic got into the habit of marking upgraded basses with the blue stickers. FWIW, it's as quiet as my upgraded basses, although some of my pre-upgrade basses are dead quiet, too. Also, the owner told me that after receiving the bass he thought about redoing the treble control frequencies and actually discussed it with someone at Alembic but never followed through. Had I used the bass more than I did I probably would have done that, using Alembic's standard bass and treble center frequencies as my guide.
Glad you are enjoying the bass!