diagonal mark vs shilling mark

diagonal mark

noun
  • Synonym of slash as the forward slash ⟨/⟩ and sometimes also its proscribed sense inclusive of the backslash ⟨\⟩. 

shilling mark

noun
  • Synonym of slash ⟨/⟩ in its use to mark the amount of shillings in a sum or (obsolete) in all its uses. 

How often have the words diagonal mark and shilling mark occurred in a corpus of books? (source: Google Ngram Viewer )