The good news about aid climbing rating scales is that the whole world uses a single scale that goes from A1 to A5. The bad news is that there are many interpretations of that scale. It will all depend on where and when that first ascent was made.
All placements are rock solid and easy.
Placements are still bomber, but the placements are awkward and a few difficult may be difficult. Many placements are difficult, but there is the occasional bomber piece. There are several placements in a row that will hold nothing more than body weight. In Europe , where most aid climbs were made long ago, this scale may be adjusted downward. Put simply, A3 placements are difficult, but will hold a short fall.