The 10mm heavy frame would have modified the 10mm pistol. There is a .44 Revolver Heavy Frame weapon mod which increases a weapon's condition by +50%, so this mod would likely have had a similar effect.
Visually, the upgrade alters the 10mm pistol by increasing the width of the upper (slide) portion of the weapon. The textures for the weapon remain unchanged.
The upgrade remains in the form of meshes, textures, and static world objects accessible in the GECK, but not as a usable mod that can be added via the console on the PC.