How to handle changes in symbol code at the time of company name/code changes in NSE (ex: Orient refractories recently got renamed to RHI Magnesita and hence its symbol code also got changed from ORIENTREF to RHIM. 

To get consistent historical data feed - can we rely on FyersToken field in the Symbols CSV ( https://public.fyers.in/sym_details/NSE_CM.csv) - will it be mapped to same company every time OR is it a dynamic token and can be assigned to different companies on different days ? If this can't be used - can ISIN code be referred for same purpose ?