First thing to consider when you receive the posts that are surely to come is that local areas call the same gravel different things. While building driveways we used about 4 different limestone plants to provide materials. They are all within 20 miles of one another. They all used the same desiganations for the materials(i.e. 10-b) however, each plant had a different type of material for their designation.
The experience that I have with driveways may not be applicable to your situation. When we build driveways, the driveways must be able to withstand loads up to 100 tons. These driveways are often through wet swampy areas that would normally not be chosen for normal driveway construction. Therefore we use alot of base while constructing a driveway. When we are topping a driveway it is more often for the purpose of smothing rather than strengthening. That said, when we are "topping" we use what is normally referred to in this area as 2A modified. Which is material from 2 inches down to powder. It adds some strength, but because it also has the fines, it also provides a nice finish once compacted.
If you are trying to smooth an existing driveway, there is one point of advive that I would like to make. Before adding material, the existing material must be loosened to a depth equal or greater than the existing low spots/ potholes. The reason for this is, that if just fill the low spots eventually the new looser material will be forced out of the low spot and be built up around it. Thus creating an even greater lowspot.
I don't know if my experiences will be applicable or not but I hope this helps some.
Jimmy