Something interesting that I've never seen discussed before. On the 2012 mod release of Black Mesa, in the models folder, there are images, autogenerated by hlmv, of almost all the models in the game. However, the images are from before the mod release, and according to the time stamps on the files, were from July 4th 2010. Here's an example of how the viewmodel for the glock and the battery item looked back then. These are just some examples, there are literally hundreds (865!) of these images.
This also applies to HL2. With combine_super_soldier.mdl showing a completely different model.
repost in black mesa
Whoa, the hev suit looked way lower poly, almost looks like the og model just retextured and subdivided. Probably all placeholder models, really cool