Named Game of the Year by over 50 publications, Valve's début title blends action and adventure with award-winning technology to create a frighteningly realistic world where players must think to survive. Also includes an exciting multiplayer mode that allows you to play against friends and enemies around the world.
So this is Black Mesa security guard with .357 Magnum equipped instead of the Glock.
YA FEELIN LUCKY?
Maybe I am wrong, but I think that this model is from black mesa style pack, from gamebanana. It is just retextured to have normal Half-Life textures instead of Black Mesa styled ones.
Gamebanana.com
Moddb.com
It is, with default textures.