The Valve Hammer Editor 3.5.2 is the last unofficial mapping tool for the Goldsource engine (Half-Life 1 and his mods) based on the last beta 3.5 made by Valve.

See the readme file for the full changelog below:

Changelog : Readme_PACK.txt

Download : Valve_Hammer_Editor_3.5.2_Setup.exe****Update 11/30/12: Update compilers tools Vluzacn 30.

Download : Valve_Hammer_Editor_3.5.2.zip

Screenshot of the interface.