Looks like a J.P. Sauer per- WWI stock that's been refinished with a nasty modern finish. You should strip it, have someone clean and go over the checkering, using the correct type tool, and refinish with oil. Looks like someone replaced the buttplate, too. It probably had a horn plate that was broken or worm eaten and replaced with the current one as it doesn't look like it fits very well. I don't blame you for going to all the work to keep the stock, those pre-war paneled Sauers handle great!