Caliber is the diameter in decimal inches. Let us know what you get. If it is a .52 caliber, it will be 52/100 of an inch. I find it easier to measure it in mm and convert to decimal inches.
I measured it with a caliper and came up with 51- 55 100th. It has a flat spot where it kind of flopped in when it landed. The weight is around an oz. also around 30 grams, my scale is not digital. Thanks
JDD