Over several years I have purchased a little bit of bitcoin here and there.  I think most, if not all, of those purchases were made on Coinbase.  I don't see any historical record of those purchases.  Is there any way to tell when, how much, and at what purchase price I made those acquisitions?  Any way to tell from the blockchain?  I don't need to know for this tax year, but I will at some point of time in the future.