53 grams equals approximately 818 grains. Very few civil war bullets are 800+ grains ...so that excludes even most (but not quite all) of the .69-caliber types. The photo you posted of your minie-bullet does not show any body grooves (a.k.a. "rings") encircling its base. If after thorough washing it indeed has no body-grooves at all, it is a rare "Pointed-Nose" .69 Tower minie.
By the way... a similar-looking grooveless .69 so-called "Prussian" (now known to be an incorrect name) weighs less than 750 grains, so your minie is not that type.)