A testpiece is the hardest MF'er possible at the Grade.
Unfortunately Kevin McLane has destroyed most of ours at Squamish. A good exception is Orifice Fish, 5.9. Or Another Tourist In Traction, 5.9 Or even Payanoia 5.9
I read somewhere 5.9, 5.10+ and 5.11d are the most common sandbag grades Reluctance to go up the number. Nowadays the trend is reversed, 11c gets called 12a Looks good on your 8a.nu scorecard
We still got em in the alpine though:
Yak Crack - original grade 5.8
South Ridge of Gimli - original grade 5.7
Widowmaker Arete - originally "4th and 5th class"