Awesome post and amazing coins. I've always had a fondness for those short reigns, and the Year of Four emperors in particular. The Galba sestertius I once owned was rather more modest in quality, but I was pleased with it, for less than 300 bucks.
Then it must be truly breathtaking indeed to hold that piece in hand and feel its heft. I just had to go back to the OP for a second look. Normally I'd have been so aureus-struck that I'd have had eyes for nothing else you posted, but the fact that your sestertius stole my awed gaze from a Galba aureus says something.