The hole is pretty much round , with the edges voided as though it was drilled from the inside out. Does it go all the way through?

However it got there , it is there now. If the grips are original to the gun I'd repair them. Pretty easy diy project to just get it filled and faired , might want to start with a wooden plug. If it were mine I would not want to leave it as is ... but your gun / your call.

Welcome aboard , fine revolver. Truly fine.