EDIT: Mind, that's my opinion as to who's making it. Not stating it as fact, just what seems apparent. Not sure if these Newegg photos are accurate but that layout is really distinct and uncommon.
I think it is a Solidyear. Using Taiwanese romanization rule, their name could be written as HY.
Just looked at some of their other keyboards and I think you are right. Anyway, definitely NOT iOne 
As I mentioned, it's possible it's old NEC stock, yes.. but that would also rule out RX200. So it's extremely confusing to me. Renesas' website sucks though, so it may be a lower end QFP48 part. Any RX200 is guaranteed to be Renesas badged though, as the part was introduced
after the split was completed. I'll do some digging around and see what the other possible parts are.
I also would agree the solder work is not bad. I wouldn't call it 'good' much less 'excellent,' but it's definitely not bad. It will hold up just fine, but that pin bend bothers me, and there's some solder slag on the PCB - which should never happen. All the quality soldering in the world won't help with a shoddy PCB though. The ripples I saw there I've only seen on low quality PCBs with poor bonding between layers. That's a serious problem for obvious reasons.
I disagree that Solidyear is more likely - the part numbers do not match their scheme. All Solidyear PNs are 3+4 Letter+Number scheme. e.g. it should be 'HYx-6004' not 'HY-6004.' Doesn't fit the numbering scheme either. They also do not have a stock PCB that maps even remotely near it. I would rate them very unlikely. So I wouldn't rule out iOne entirely yet. Again, iOne can modify existing designs to meet customer requirements. So that means that it could be a modified Scorpius. But again; I don't see any evidence saying explicitly that it's iOne. Just a collection of circumstantial that it's an iOne design.
Also, remember that Thermaltake Meka covers multiple keyboards. The G1 is literally a badged CST-104 "Sydney" reference. IIRC there's 5 different ODMs.
The cabled controller isn't entirely red herring, either. The CST104 can be cabled instead of push-mount, but that would be a new PN. But it's also uncommon as hell these days - so who do we know that uses cabled controllers? I can't say I know anyone these days.
EDIT:
Digging into things a bit, it hit me that being 48TQFP, it could be a part I'm very familiar with - the NEC uPD72010 USB 2.0 Controller. Every uPD72nnn is NEC badged or no mfg badge, even current. This is a
current uPD72010 photo and
here's the datasheet (Warning: PDF). However, that would mean it's
not the microcontroller itself - the D72nnn's strictly a hub.
The other possibility might be that it's a M66291GP which
is a complete microcontroller. No photo for this one, but it's actually a blended NEC/Renesas/Hitachi part which is
currently made and has a
datasheet here. (Warning: PDF)
