top-grade vs top-level

top-grade

adj

  • Of the highest quality. 

top-level

adj

  • Best. 

  • Highest. 

  • Applied to domains at the highest level, such as .uk covering all sites for the United Kingdom. 

noun

  • read-eval-print loop 

How often have the words top-grade and top-level occurred in a corpus of books? (source: Google Ngram Viewer )