The Sandtroopers are seen on the sands of Tatooine in A New Hope. They have a variety of features that separate them from the clean white stormtroopers in the other films.
The Sandtroopers are seen with ammunition pouches on their shoulders and belts. Typically these are MP-40 pouches, in either leather or canvas. Many 501st troopers will use a larger, inaccurate pouch on the belt to hold a voice amp, wallet, or other personal effects. It blends nicely with the costume, and is a practical addition to the suit.
Sandtroopers are seen with a colored pauldron worn on the right side. It is believed to be old BMX chest armor worn sideways. This same armor is seen on the Imperial Gunners, worn properly on the chest. The sandtroopers were seen with black, white and orange pauldrons. Hasbro produced a greay pauldron trooper as a Dewback rider, but the general consensus is that the dewback mounted troopers just had very dirty white pauldrons.
Most sandtroopers wore a field pack, made up of a variety of items. Tupperware containers, spare parts from the stormtroopers' thermal detonators, and other found items of the day. Check out http://www.mepd.net (the official 501st Sandtrooper Detachment) for specific information about the components of the pack.
The pack shown here was a work in progress.
The weapons used by the TDs varied quite a bit. There were 3 real-world weapons used almost exactly “as-is”:
Each of these weapons had scopes added and greeblies attached, but are basically “off the shelf” vintage military weapons.
On first glance it looks like the sandtrooper helmet is just a stormtrooper with dirt, but that is not correct. The teardrop and rear decals on the stormtrooper helmet have black stripes, where the sandtrooper ones are plain grey. The sandtroopers have flat green lenses like the stunt stormtroopers (i.e. should not have the bubble lenses found in a hero stormtrooper). Sandtroopers also have raised brow trim, also like the stunt stormtroopers.
On the stormtrooper abdomen, there are 2 areas with colored buttons. The sandtrooper is completely missing the center detail plate, and the smaller one has buttons, but they are white.
Sandtroopers have a diamond shaped plate on the right knee, vs. the much more detailed one on the stormtrooper.
stormtroopers have white boxes hanging from their belts, possible to help cover up the gaps in the armor at the hip joint. Sandtroopers did not have this, possibly due to the ammo pouches worn on the belt.
No sandtrooper is seen with an E-11 holster