The "funny bike" in question is in no way a Turbo. Having had 2 Turbos and now having one of those funny bike frame sitting here, of that I have no doubt.

As far as it being anything similar to a WSI US-market Turbo, just no way.

Per @T-Mar, the serial number pegs it to a time when WSI was shutting down their vendor's production of Centurions for the US market. I have no idea what they were doing in other markets.

The frame appears to use the same BB shell as the Asian market Dave Scott that @seypat owns. The dropouts are Shimano SFR, which I've not seen on a Centurion. The paint and finish are very consistent with the specs that WSI ordered for at least their '86-'89 models. The decals are consistent with a font scheme used by '84-'85 Centurions, but are trimmed a bit differently, kind of a mix of the '84 and '85 font. The lugs elsewhere are quite similar. As we all know, lugs are lugs, in many cases, and one batch can be slightly different than another.

Whoever made it, it is clear that the intent to, at the very least, mimic the characteristics of a WSI Centurion is there. Those of us who've handled multiple nice Centurion and Ironman frames would likely agree, given the chance to hold it and examine it. Doesn't mean it wasn't mimicking a Shogun or Bridgestone or Panasonic of the same era.

With apparently none of the OEM 650c forks for this frame around, I'll make do with a Zunow 650c fork, stripped and painted to match, with the panto logos on the fork crown filled in. Wouldn't want anyone accusing me of repainting a Zunow to look like a Centurion.

Unless I see evidence otherwise, I'll stick to my opinion that there is some connection to WSI in this frame. Its very similar, so if it wasn't spec'd, maybe permission was granted, and maybe just tolerated. Don't really know, don't really care. I can't see why someone would create multiple frames, paint them so well, add the decals, clear over them, then take the time and trouble to add the Tange decals, and the "Japan" logo on the frame, that uses the same script-type font as the Centurion WSI lower ST decals, with no connection. Perhaps there's a bigger Centurion flake than me, hiding and building in a small frame shop in Europe, only coming out 30 years later to fool us all with this frame. Yeah, that's it.