That centre hole of the three has had a "flat" either filed off or otherwise removed. If you are going to try to re-finish that, will likely need a "patch" installed - maybe like a "dutchman". I have robbed "patches" and also have cut short "taper plugs" from inside the barrel channel on a stock - to repair a hole - thinking to match the grain and wood species - then the "robbed" places were filled with bedding epoxy when I bedded the action into the receiver. Some others have also successfully "robbed" from behind the butt plate at the rear of the stock. Beyond my skill level to make such a patch "invisible" - but I have seen repairs on older fine furniture that are very difficult to see that there is a repair - I am sure that is all about matching up the wood grain and wood species so they respond similarly to the stain and finish that gets applied, and very close fitting - to the point there is virtually no glue line exposed. The normal "hardwood" dowels available at hardware stores out here can be used to "fix" the hole, but I have had very little success in matching that exposed end grain to the parent rifle stock.