I acquired a stock for a Ruger rifle last Friday at an estate sale. I've no idea which model of rifle that it would fit. I know it's a Ruger because it has a Ruger medallion as a cap on the pistol grip. I'm not sure of the wood, walnut or maybe maple. It has an opening for a clip or hinged floor plate. It looks to be new and unused. How the heck do I figure out what I have?