Thank you for the bullet's super-precise weight. Its 353-grain weight proves it is absolutely not a .44 or .46-caliber bullet. For example, a so-called .44 Kerr 3-groove minie is longer (.93") than your .89" minie, but it weighs 83 grains less than your minie.
Another .44 Kerr version (bullet #439 in the M&M book) is .91" long, and weighs 225 grains, which is 128 grains less than your minie.
The .46-caliber (note .46, not .44) Remington minie in the M&M book (bullet #444) is the same length as your minie (.890), but it weighs 302 grains, which is 51 grains less than your minie.
If you check the McKee-&-Mason book for weights of various .54-caliber minies that are very close to the same length as your .89" minie, you'll see they weigh very close to your minie's 353-grain weight. (For example, bullet #433 is .90"-long and weighs 372 grains -- it's a tad longer and weighs only 19 grains more than your bullet.)
It is scientifically impossible for your 353-grain, .89"-long minie to be the .450-to.455"-diameter you say it is. That's why nobody has been able to ID it, despite a lot of research labor.
I suspected that, back when I first examined the photos you posted. Which is why asked you to put a ruler up against the minie's base to see if it really is less than .5-inch wide. If your bullet is indeed actually .45 in diameter, the guy holding it has the smallest thumb fingernail I've ever seen on an adult male. And that still wouldn't explain the length-versus-weight paradox.