It reads "T.85" T and both 8 & 5 are individually underlined,
see pictures.
The salt is a recent addition to my little collection of salts which I use for instruction purposes (As a metal conservator/restorer I give courses on several subjects, including a course on cleaning of silver at the ICN, The Netherlands Institute for Conservation).
Any information on origin of this mark would be appreciated, also information on why this salt would have only 1 mark would be appreciated.
Michiel Langeveld

