In 1967 York Minster underwent an extensive programme of engineering works to consolidate the medieval fabric, which tests had shown to be essentially unstable.
Archaeologist Dr John Dent FSA was asked to record any traces of monumental brasses which the lifting of the floor might have brought to light. He recorded several fragmentary indents cut into Frosterly or Purbeck marble that had been cut up from earlier grave slabs when the floor was re-laid in the 18th century. He made graphite dabbings of these. He also made a rubbing of a fragmentary brass inscription, the present whereabouts of which is unknown. These dabbings and rubbings are the ones made of the material, all of which is no longer available for study.
See: “New light on lost brasses in York Minster” by John Dent and Sally Badham in Transactions of the Monumental Brass Society XIX, Part 3 (2016), 235-248.