candidate reference material 

Synonym: candidate RM
https://doi.org/10.1351/goldbook.08060
Material subjected to the procedures necessary to show its fitness for intended use (see fitness for purpose).
Note:
A candidate reference material for a given property may already be a reference material for other properties.
Source:
PAC, 2021, 93, 997. (Metrological and quality concepts in analytical chemistry (IUPAC Recommendations 2021)) on page 1021 [Terms] [Paper]