The model viewer created for and used by Bloodbath Software.
Bloodbath Model Viewer 0.19 by eukara
Based on the Half-Life Model Viewer by Mete Ciragan, BBMV adds various improvements and features that are present in similar (proprietary) forks. The source code was recently found and is now provided, hence the new upload. This was separated from Overturn's SVN upload for convenience as well.
Bloodbath Model Viewer (c) 2014 by Marco Hladik
Half-Life Model Viewer (c) 1999 by Mete Ciragan