Probably a welch plug (think: mini "freeze plug"). I remove them by drilling a small hole in the center, threading a sheet metal screw into the hole and using a claw hammer or wonder bar to prey it out. Use axle grease on the drill bit and sheet metal screw to prevent metal shavings from falling into the engine.As shown earlier, I have swapped my oil pan to a rear sump instead of front sump. Never gave a thought about the dipstick until reading a post the other day that spoke about moving it to the rear hole. What is involved in doing that? I see the location, but havent poked around in there yet. Hopefully I dont have to finish drilling the hole as my pan is on and the oil is in. Allen plug?