The Express synthetic used to be named the "Home Defense".
It's a lower cost version of the Wingmaster sporting gun and the Police gun.
The only real differences is that the Express has a rougher finish inside and out with machine marks and some burrs left in place.
The extractor is made of MIM steel, but that's easy to replace with a milled part from the Wingmaster or Police models.
Where the Wingmaster has a polished blue finish and the Police models have a parkerized finish, the Express has a bead blasted flat blued finish.
Other then that, the Express uses the same forged steel receiver and heavy duty fabricated internals the more expensive 870 models have.
Just like the more expensive models the Express 870 will last several lifetimes in heavy use.