Rub your finger across the current paint. It should come off fairly easily, if it is standard AF paint. Harder AF paint exists and will not rub off so easily, but it is fairly rare stuff.
If it is soft bottom paint, you have narrowed it down. It could be soft copper paint, mostly used on slow displacement hulls, or it could be standard single season modified epoxy paint or it could be ablative AF paint. The latter two are used on most planning hulls.
So what kind of boat is it on? If a planning hull, it is likely ablative. Of course the final step is to take your best guess, buy some paint that is supposed to be compatible (most of the same types are compatible) and try it out in a small area.