Aluminum debris in oil

Thanks for the input guys, I've looked into the case from the bottom and haven't been able to find any obvious signs of damage. Maybe ride it and drain the oil again after some miles? 

Is it smoking or making noise?
Steve

Neither from what I can tell

I'd pull the engine and split the cases.  Too much unknown.  

If the engine is truly running fine. Is it possible this is left over from an upper end rebuild as Steve suggested. May it was rebuilt on the bike and the broken items fell into the cases.