I sometimes see it on ply here.I like to use marine ply when building things for the hens and I try to buy AA which means there are no blemishes in the grain on either side and that's good because blemishes are more likely to hold water. Sometimes AA is not available and sometimes I can't afford it. The new ramp was made from a BC 3 ply I bought when working on the roosting box. So it's got blemishes on the B side, and significant blemishes on the C side (quite large knots).
Is the A B C ply grading system in use elsewhere?