Made by NMB. (I realised that from the FCC ID before I even got the pictures at the bottom showing the characteristic sliders.)
Interestingly, that's in NMB's 6600 (low footprint) series — some NMB OEM boards have weird model numbers that don't fit their RTnnnn pattern (e.g. Dell RT7D50, Logitech Y-RJ20 (RT7R04)) — maybe one day I'll figure out the meaning behind these.