I have a list of bond ISINs for which I require historical spread data. My current approach is to use ek.get_data to obtain 'Bond RIC' and then use rdp.get_historical_price_summaries for each single instrument.
My questions are:
1. Why are some Bond RICs not unique per ISIN? E.g. FR0010678185 and FR0010695171 have the same Bond RIC 'FR00140046Y4=JFTW'.
Is there another specific Bond identifier that is unique and better geared for my purposes? Or maybe even a way to get historical spreads directly using ISINs?