Eric,
Do you suppose this particular gun has gained more than 3% per year without some discovery in provenance which wasn't known at the sale? I am going with the assumption that it has no special provenance.
That would make it $138K today with a 3% annual gain.
That might be possible but not a sure bet IMO.
And of course, I am trying to keep as little cash in the bank! Making 3% in a savings account just isn't reality right now.