Source for Test Lab to measure the appearance (specular, DOI and diffuse reflectance) of mirrors and mirror-like surfaces
The test method most applicable for specular gloss and DOI of mirrors is:
ASTM E430 Standard Test Methods for Measurement of Gloss of High-Gloss Surfaces by Goniophotometry which describes the methodology used in the development of the legacy HunterLab Dorigon meter.
A company that sells a Dorigon replacement unit which is primarily a QA instrument is:
Tricor Systems Inc.
Elgin, IL 60123 USA
HunterLab does perform mirror testing and finding an optical testing lab for mirrors is not so easy but here are some possibilities.
NRC - National Research Council of Canada
Ottawa, ON K1A 0R6 Canada
Avian Technologies LLC
Sunapee, NH 03782 USA
Gooch and Housego
Orlando, FL USA 32811 USA
Lighting Sciences Canada
Waterloo, Ontario, N2V 2B1 Canada