"Interesting--even the OO grades?"

Yes according the pre-13 catalogs, the Grade OO gun was fitted with "English walnut stock; half pistol, checkered and well finished". In fact, and according to period catalogs, even the cheapest hammer gun model had an English walnut stock; but wood was obviously plain grained on lower end models. When the company changed their grades line-up in 1913 a decision was made to switch stock wood from English to the less expensive American black walnut.