Do you mean you've converted it to SG/MY firmware? JCV was dropped for SG/MY in V2.x0 for some reason, i can't remember the exact version. I do recall that EN TTS was sh*t though. Why did you want to revert to V5.70 US before cross-flashing?

EDIT: I just noticed this in your earlier post:
Quote Originally Posted by matti_k View Post
I need to downgrade my 255w to 5.70 or lower can anyone re-post?
b1091-00
If B1091-00 is correct for your 255W it's US/EU MTK chip HWID 1091. I thought only HWID 0827 non-mtk could be converted to Asian. The V5.70 supplied by Caty is HWID 0827.