The implementation of VRML97 was meant to be in accordance with ISO/IEC 14772-1:1997. I believe this was never fully implemented. However, there is now X3D and its current standard ISO/IEC IS 19775-1:2013. This is currently at version 3.3.
Making fully compliant code will involve multiple repositories. Obviously Coin is the first. It may also be necessary to incorporate SimVoleon.
Then I propose a major overhaul of SoWin (because I am familiar with it!) which could then be translated into repositories for other platforms.
Finally it will be necessary to present a complete viewer. Again, this will be initially for Windows but translatable for other platforms.